I'm just going to give Vanja and Hildigrim a chance to weigh in. No worries.

Hildigrim mimes tipping a hat to Mrs. Brinarei and sets off at a trot, scanning the area for any movement or clues to danger.

Perception: 18

Seeing the nervous sheep scattered about, and the first signs of the two slaughtered corpses in the shelter, Vanja swallows hard but nods to Drusk.

"I mean, I'm pretty good with animals, but I've never had to really examine dead ones before.  Closest I've ever gotten to that was helping clean what our hunters managed to take while we were on the road, and last time I did that was years ago.  Any help you can offer will be appreciated."

With that, Vanja will SLOWLY and cautiously approach the shelter with the slaughtered animals to see what she can discover.

Investigation: 7

Medicine: 22

Guidance Roll: 4

OOC > So, this was nice, but...

Jorin and Drusk cross the bridge in front. Drusk turns to talk to Vanja about checking out the sheep, and she nods hesitantly. As Drusk calls on his goddess for assistance, Jorin hefts his axes, and strides towards the cottage. Mrs. Brinarei moves with Criella towards the center of the area. Vanja begins approaching the sheep. And Hildigrim, last in line, steps off the bridge...

You are all still mostly clustered. Nobody has made it very far on their intended paths.

Everyone please roll a Perception check.

OOC: Dang, and that Medicine Check was so good too...

Vanja Perception: 25

Mrs Brinarei Perception - 13

Criella's Perception roll: 7

OOC > Ha! This might explain some things!

(OOC: For Vanja, I was thinking Survival (which she is good at) or Nature (which she isn't, despite being a Druid). But I should have stated that earlier. My bad.)

Drusk Perception with self-Guidance : 18 + 3 + 2 = 23

I already rolled perception previously.

Jorin perception: 9

As Hildigrim steps foot off the bridge onto the grounds of Criella's homestead, the brambles and leafless bushes to both sides of the bridge shudder and creak, as the brush rips its roots from the ground, branches coiling themselves into arms and legs before your eyes, turning into short, wooden, humanoid figures. There are four to each side, and they advance on you with claw-like limbs.

The animated brush is advancing, four to each side. Four will be attacking Jorin, Mrs. Brinarei and Hildigrim, the other four will be attacking Drusk, Vanja, and Criella. Because they are coming from the sides, there is not exactly a front line they have to get past, so they can get at all of you.

We have combat! Here is a refresher/primer on the concurrent initiative system we are  trying out.

Jorin, intent on the cabin, hefting his axes, misses the brush animating (you failed to Perceive it, and have defaulted to Delay, and will be able to declare after everyone else has resolved. This is the equivalent of being surprised, except you'll get to go, just not until after everyone else has gone). Criella, too, misses the transformation as she stares once again at her dead sheep. The rest of you may declare your actions.

Concurrent Initiative intro and/or reminder

Concurrent initiative is meant to get away from the problems (I have) with cyclical initiative. Very simply: everyone declares their intentions, then the DM resolves those actions logically, with some rules thrown in to manage anything that happens simultaneously. Players can Declare their actions, with conditional caveats within reason, or they can Delay.  Here is the longer version: https://www.dndbeyond.com/campaigns/277586

Specifically for PbP, here’s what I want you to do each round.

In your post:

• Declare what your character intends to do in the next round (six seconds). You can Delay, or you can make conditional declarations. Declare any or all of your Action, Move, Bonus Action, and/or Reaction you want to use.
• Roll an Initiative roll, in case I need it.
• Roll for whatever you’ve declared you will do, (skills, to hit, damage, etc.) in case I need it.

Remember, this is intended to be fun. If it is not, let’s talk and tweak. Thank you for agreeing to be my guinea pigs.

OoC: Excited!  So, to clarify, Jorin has defaulted to delay, so I'm out this round and I'll be acting in the next.  Am I understanding correctly?

Jorin Initiative:20

Drusk is picking a side, preferably away from Jorin. Trying to block the 4 on that side so they can't attack the squishy members of the party. And a swing from "Joybringer" at the closest one, for good measure.

Mace swing - Attack: 17 Damage: 6 bludgeoning

(Edit: Forgot the initiative! 18 )

OOC > Not exactly, Jorin will get to act in Round 1, he was "surprised" which in this system means he took the default Delay action. Delay means he declares (and acts) after everyone who does not Delay declares and acts. So you'll declare after I've posted the Round 1 summary. So will Criella. Then I'll add that to the Round 1 summary, and we'll go on to Round 2. You get to see what happens, and react to it in the same round, but everyone gets the drop on you.

I'm still figuring out how I'm doing this (first time DMing PbP), so here's what I'm thinking. I will always (unless special circumstances) declare the monsters' intent before asking you guys to do so (as I did above). I think it is above board to then also pre-roll their rolls, as I'm asking you guys to do. All these rolls might not come into play (say one dies before acting), as might be the case with your rolls. Then I'll hash it out in the resolution post. So...

As previously mentioned, the eight wooden stick men advance menacingly, four to a side.

Spoilering monster rolls...

OoC: got it!  Jorin will declare after the round 1 summary gets posted.

Quote from Mingofaust >>

I'm still figuring out how I'm doing this (first time DMing PbP), so here's what I'm thinking. I will always (unless special circumstances) declare the monsters' intent before asking you guys to do so (as I did above).

 (OOC: I think you should wait until after we declare. Or put it in a "spoiler" block and ask us to not look at it until after everyone states their action.

I had Drusk trying to absorb the hits of the 4 on his side. But I did this knowing that enough bad rolls would knock him out. If I see that all 8 of them would miss, like they do in this case, then I'd be bolder than reasonable.)

Quote from Quasimodal >>

 (OOC: I think you should wait until after we declare. Or put it in a "spoiler" block and ask us to not look at it until after everyone states their action.

I had Drusk trying to absorb the hits of the 4 on his side. But I did this knowing that enough bad rolls would knock him out. If I see that all 8 of them would miss, like they do in this case, then I'd be bolder than reasonable.)

 That makes a lot of sense, yes. Will do that from now on... :) Edit: and retconned the post above with a spoiler tag.

From the logical standpoint that Criella was just here yesterday and didn't react negatively toward these bush things as the group approached, nor has she reacted to their coming to life, Hildigrim is going to jump back out of harm's way (just to be safe), but say, "Criella, call off your guard, please!"

Also, I can't find anything anywhere about the help action causing DISadvantage. Can I declare that Hildigrim, besides the above (since speaking a short phrase is a free action), will help another character by shouting "Watch out!" and give the attacker disadvantage? I know from the help action explanation I would need to be specific, so I would say the following: Hildi will watch Jorin's back since he seems to not be paying attention, and when the first creature swings at him, he will shout, "Jorin, watch out!" to give the creature disadvantage because Jorin will be warned to evade the attack. Is that allowed?

Initiative: 22

(OOC: For Criella's reaction, a low perception might mean she didn't even notice new bushes on her lawn, as she was focused on the sheep. Or at least I hope so, otherwise she has just lost a guard to Drusk's mace.

For the latter part, is up to Mingofaust. In my opinion, based on what is in the PHB pg 192, it only mentions advantage on an ally's ability check, or an ally's attack roll. Yelling "watch out" wouldn't be fast enough to help someone react to a sword swing or a monster claw, or hinder such an attack. You would also have to be in melee range to affect combat. You could always stand in front of Jorin, hope it targets you instead, and use the Dodge action so attacks against you have Disadvantage.

Edit: If you still aren't convinced, think of it this way. Jorin is defending himself against the twig man in front of him. He hears "Jorin, watch out!" Is Jorin going to react to the twig man's attack? Maybe it is a feint, and he should be watching for some special ability? Or maybe he should turn around, because "watch out" meant someone was sneaking up behind him? Those words won't really help Jorin or hinder his opponent.)