I’ve got competitive tree felling, log flume riding, and caber tossing. There’s archery and boxing/wrestling. There’s chess, there’s a pie eating competition, even an obstacle course.
That gives me all the mechanics I’m interested in settling the players into immediately - ranged and melee attacks, skill checks, saves, skill challenges, and roleplay - but I need more fun side bits to help set the scene. There’s food stalls, a bar, a little gambling, and I’m probably going to have a children’s storytime place the players can go and make up wild tales, but what other kinds of flavour do you pepper around your festivals for the players to interact with?
The campaign is Abomination Vaults for anyone with setting specific ideas.
Have a big monstrous beast on a skewer over the fire, like a giant spider or an ankheg. The cook might be struggling to carve it up, or it might be a contest of who can eat the whatever gross bit, or the monster catcher is telling lies about how they caught it to bask in glory.
A griffin cub or similar small flying beast is being used to give children rides. Maybe this is under duress, maybe the beast likes doing it against the wishes of an older and more dignified member of the same species. The beastmaster may mistreat the animal or might be protecting it from some worse fate. Talk to animals is important here.
Marketplace filled with oddities from far away. Maybe underground dwellers wrapped in heavy cloaks to keep the light out of their eyes are selling mushrooms to surface folk.
Pickpockets are out in force. The party spots one in action (or has their own stuff stolen) - do they seek justice or let it slide?
Tarot reading/fortune telling. This is a fun way to advance player character plots or give yourself a hook to use in the future as GM.
Fish out of water - if this is predominantly a peasant/villager affair then have a carriage of nobles show up to gawk. If the other way around, Ma and Pa Kettle show up with their brutish country mannerisms.
Fireworks - everyone loves fireworks. Have a fireworks person who will sell sparklers to the kids but is holding on to the big ones for the finale at the peak of the fair. Will they last that long before the party tries to steal them/set them off/use them as a distraction?
Fantasy themed candy/treats are good. Make it weird, make the townsfolk thrilled that this special vendor is back - everyone loves candied cranium rat on a stick.
Finally, think about whether or how this ties into your broader campaign. A festival can just be a playground for your players, but they could also know that someone they need information from/need to kidnap/kill is with the festival but they don’t know who (meaning they need to ask around and talk to different people). Maybe there is an object they want to steal from a guest. Maybe the map they need is a prize to be won from a ring toss contest, and there’s a child ringtoss prodigy that is running the table.
Unfortunately quite a few of these roles are already taken by campaign NPCs, and I don’t want to open the campaign by taking player’s meagre belongings, but I’ll definitely be stealing the monster roast (it’s a seaside town, so I’ll use something aquatic) and fantasy candies, they sound great.
The festival is solely a playground for the players to get used to things, before the campaign-triggering event as dusk falls. The module opens with the PCs already investigating spooky lights from the old abandoned lighthouse, but I want to give the town it’s in and the PCs some characterisation instead of jumping straight into initiative - every NPC I have at the festival so far is someone who will (/can) help the PCs later once the plot gets going, and they’re going to stay in the same town for all 10 levels so I want to give the players a personal attachment to the place and people.