6 lvl 12 pcs Djinni warlock, alchemist artificer, aberrant mind sorcerer, war mage wizard, devotion paladin, and totem barbarian/5 moon druid 7 its a lot of people

Both the barbarian and paladin are sitting on 21 ac

They are currently on a boat headed to a jungle area, thoughts on some fun encounters?

Purple people eaters.

seriously .

they are purple skinned, one eyed, one horned, short shorts loving, rock and roll playing small humanoids who gore their victims and then feast. Eat enough and they grow to eight feet and can swallow a small or tiny whole.

they can be bought off with new music or a bunch of short shorts.

use fiend stats.

play it totally straight, dreaded small creatures in the deep jungle, terrifying villages by playing the horns on their head in horrific music, speaking strange words like bomba bam, and see of the players twig to the idea of using music or throwing clothing.

if they do twig, then you will have a session to remember 

can i get a link cant find them

I will brew something up tonight after work for ya, then put the link here.

pin the tale on the donkey

hit the pinata 

blow out the birthday cake. 

Well, it kinda depends on the situation as to what would work best for you, but here are a couple of options to consider.

They find a magical orb, which they set off by touching it, sneezing on it, or whatever else is needed to make it happen. The orb then creates a portal to another dimension and this portal creates a temporary vacuum sucking them into it. They find themselves in an unusual world, I'm thinking kinda Alice in Wonderlandy, but with an outer space looking atmosphere, but you do you. Here they search around and you can have various malicious affects hindering them, noxious fog, poisonous mushroom spores spitting at them out of alien mushrooms as they walk by, quick sand traps covered by a thin layer of moss so they are hard to see. Long story short, the adventure becomes about finding their way home, and to do so, there could be many possible encounters here, but it might be a great set-up for them having to ultimately fight a mirror image of themselves, but evil aligned versions. Perhaps, the evil beings sent the orb to their dimension, b/c they cannot travel and then remain/live their indefinately, unless they have first brought alternate versions of themselves to replace themselves in their dimension. Ok, so that's out there, but it's an idea.

Something a little more run of the mill would be, there is an evil horde army spawned from the abyss come to attack a village your PC's know. To complicate things, the horde has started a forest fire in a nearby forest that will endanger countless lives. This could include but is not limited to: Elves, Centaurs, Sprites, Dryads, Treants, and general wildlife and vegetation. If you still want to kick it up a notch, the horde may have also spooked a nearby herd of what are now rampaging catoblepas's (death gaze and all) that are tearing their way through farmlands destroying crops and causing general chaos and destruction. Your PC's now need to quickly decide what to try to solve first, or perhaps, they could split up (insert evil laugh here). lol

Anyways, there are a few ideas for you, hope that helps. I didn't really worry about checking CR ratings, as a lot of times it is more about the situation that makes things difficult, than the CR itself, but feel free to use or not and make changes as needed.

Have fun!

I am not gifted at using this system, but…

https://www.dndbeyond.com/monsters/3308594-mites

A standard set-up I have is that the players encounter a small homestead/hamlet in a woodland clearing there are two building which appear to be on fire: 

Upon investigating the party notice that the fire isn't hot, or making a noise. If the party enter through the gap in the wooden fence they discover the flames are an illusion:

Inside this settlement reside a handful of nature loving humanoids who protect some sort of magical artefact. They have recently been under attack by some (level appropriate) enemies such as Orcs. While the residents have repelled the two groups who attacked, they are fearful that the Orc Leader is going to continue sending her soldiers. So the residents set the illusion to make the Orcs think that the residents have fled.

The residents need time to prepare the magical artefact for transport. The party now have five (real life) minutes to prepare to repel the next group who are going to arrive.

As a GM I run this session as a mini siege, the group have some time to prepare defences and then repel a wave. In all I usually throw a few waves of enemies at the group. In my case I threw 18 orcs, and 6 dragonborn at the party in four waves. Between each wave the party had time to recover and redefend the area. The maps for reference are designed for a 40x30 grid, but you could easily scale up or down depending on needs. 

In the two sessions run recently for my groups, so far players have stretched the legs of their illusion and other little used magics. I've had all sorts of creative solutions to defend against waves. And it's sort of rare that players get the chance to really set up and defend an area in this kind of way. The real beauty is that you can throw almost whatever you want at the party and in whatever order. If the novelty has worn off after just the first wave, throw a second one at them and then have the residents declare they can now safely move the artefact. Again the artefact can also be anything of your choosing. The residents may have some useful items as rewards. That's all up to you. The real fun thing is that I feel like this set up can be setting or system neutral.