Ben:

Initiative:  8

As the figure reveals itself, Ben steadies his scavenged shield and puts his hand on the hilt of the tiny buy finely-made sword.  He looks at the jolly miscreant and says, "We hear you've been naughty, stealing truffles and causing mischief.  Assault us at your peril!"

Intimidate:  21

Matilda Initiative: 8

She raised an eyebrow at Horatio and tried to move towards the skiff staying as quiet as she could...

Horatio: Initiative 11

Seeing the others in peril, Horatio follows Matilda's lead toward the skiff.

"Wait! We just want to talk!" Titaani says, hiding behind Ben's shield. "We're patrons of the Archfey Titania. For your own sake, think before you act!"

(Not sure if Ben needs help with intimidation but I think that comment can be used as help in case)

Initiative: 6

(shoot I forgot to highlight Titaani's dialogue. I'll edit the post and do that, so for reference my initiative roll was an 18)

Initiative:
Titaani (causeway): 18
Ben (causeway): 8
Cad (causeway): 7

Matilda (water): 17
Horatio (water): 11

Agdon Longscarf (presumed): 20
Brigands in boat: 6 

Longscarf finishes his song but then pauses at Ben's bravado, followed by Titaani's remarks.

"Assault?? Never. Talk? Well, responsibility isn’t really my thing.”

He darts forward with incredible speed, his bright blue scarf trailing behind him, and tries to brand Cad with his hot iron.
Branding Iron Attack #1 vs Cad: 25  Hit: 6 fire damage
Branding Iron Attack #2 vs Cad: 11  Hit: 11 fire damage
Other shenanigans: 26

Cad feels a searing pain as a firey brand is stamped upon his chest. (The brand it makes is shaped like three bounding rabbits connected nose to tail, forming a triangle.) Only his arcane armor stops the second brand from taking him down completely.

"A thousand pardons" mocks Longscarf as he jumps away in a massive spring. (Cad, Ben, and Titaani may get an opportunity attack as he does.) Longscarf is holding Cad's tankard in his other hand, which he must have fished out of Cad's pack in his lightning-fast attack.

Cad, Ben, and Titaani may take an opportunity attack if they wish.
Cad, however, is confused - the cocky harengon is gone; completely invisible to his eyes (make attacks and opportunity attacks at disadvantage.) The others can see him fine.
Titaani and Matilda may act next.

Cadwallader:

Cad is astonished at the unprovoked attack. He clumsily swings his staff at the thief, who seems to have fled.
Quarterstaff attack: 7 for 4

Ben:

Astonished at the knave’s attack, Ben lashes out with that tiny sword, trying to slice at Longscarf as he bounds away—if he gets lucky the thief may drop his newly stolen loot…

Tiny Sword Attack:  Attack: 17 Damage: 4

Cad whiffs the air with his staff, his back turned completely to Longscarf. Cad has no idea where he is - the bandit leader is completely invisible to him (and to him alone.)

Ben, who can see Longscarf plainly, comes much closer. But in addition to having studded leather armor and a small shield, the harengon boss is extraordinarily quick, and just dodges Ben's small blade.

Titaani may take an opportunity attack if she wishes, and Titaani and Matilda may both act.

Titaani will take her opportunity attack. 

Casting a concerned look at Cad, she turns and glares daggers at the blue scarfed bandit. "You...you..."

With burning anger, she throws her boomerang towards him. 25 (if hits, 7)

"You jerk! Don't hurt my friends!"

Hearing something kick off with her friends who were ' talking' , and fearing the rabbits aboard the skiff would overwhelm them, Matilda did something stupid.

She snagged a measure of knitted wool from her toolbag, dipped it into the water to make it heavier and threw it at the head of the rabbit steering the skiff.

20

(Titaani may still have her opportunity attack; it must be with a melee weapon like a dagger or unarmed strike.)

After Longscarf hops away, his scarf trailing in the still air, Titaani lets loose with her boomerang. It clobbers the harengon leader right in the head. A direct hit! Crit damage: 1 bludgeoning damage. 

"Owww!" Longscarf looks hurt and upset, shocked that anyone would do such a thing to him. He glares at Titaani. The boomerang falls wetly into a pool below. He looks stunned and not trivially injured, as well as upset.

Matilda winds up her arm and throws a wad of wet wool at the skiff. A wild throw, it goes astray immediately, and smacks Horatio in the eye, instead.

It does, however, catch the attention of the occupants of the skiff, which might have been her intent anyway.

(Skiff crew up next.)

Matilda and Horatio can see that the skiff contains two rowers, a lookout, and a bagpiper - all harengon brigands.

The lookout lifts a light crossbow, and fires a shot at Matilda.
Light Crossbow Attack: 15  Hit: 8 piercing damage.
Immediately after making this attack, the harengon sniper ducks under the edge of the vessel, trying to hide from view. Stealth: 23

The rowers, for a moment indecisive as to which way to go, choose to continue toward the causeway supporting Titaani, Ben. and Cad. They arrive, and three of them hop up onto the causeway, clubs at the ready. The sniper continues to hide in the skiff.

Horatio, Ben, and Cad may act. (And Titaani may also still have her melee attack vs. Longscarf from earlier if she wants.)
There are three club-wielding harengon on the causeway, within fifteen feet of Ben, Cad, and Titaani. Longscarf is on an adjoining causeway, about twenty feet away, separated by water (and a soggy but effective boomerang.)
Horatio is in waist-deep water, about 40 feet from the fight, with Matilda.

Ben:

Moving up to engage the three harengon on the causeway and block them from the others, Ben says to Cadwallader and Titiaani, "I will deal with these ruffians--you teach that knavish Longscarf some manners!"  After engaging the three, Ben drops into a defensive stance, waving the magical tiny longsword threateningly at the brigands and trying to block any incoming shots from their clubs.

Move to engage, Dodge to defend while blocking them on the causeway (if he can).

How's this for a map? (Background by FoxGloveArmor.)

Cadwallader:

"How're we supposed to deal with the leader when he's fled?!" Cad shouts, unable to see Longscarf anywhere. It's like he disappeared! Frustrated and angry, he points his staff and utters [spell]magic missile;arcane words[/skill] at the three approaching Ben.
MM1: 2
MM2: 3
MM3: 3

A bit flustered -- this is the first time he's targeted more than wooden targets with this deadly spell -- Cad backs up about 20' from the others.

((One dart at each of the three.))

Ben:

Still not completely understanding Cad’s plight, Ben points to the knave and says, “He’s right there!”

Titaani takes her opportunity attack, for real this time. Lunging forward with her dagger, she sweeps at Longscarf. 

Attack: 18 Damage: 5