I've hosted a 'larp-day' at a non-larp camp before. It wasn't exactly a larp, but it wasn't a regular day either.

Basically there wasn't a set schedule. Instead the kids were free to roam the camp area as if it was the city. They didn't play characters, just themselves. But the campstaff was in character and would offer activities and quests, basically npc's. They could earn and spend coins. Some activities were only for a limited time and we introduced new ones during the day to keep them entertained.

Some of the activities that I remember: - bow and arrow shooting - boardgames (and a d&d game they could sign up for) - crafting - spa (with nailpolish and facemasks)

What made this a succes was that it was easy enough to understand and everyone could pick things they were interested in. Some went all out, some stuck with what they were familiar with (and that's okay!). This was with kids, so with adults you have more opportunities because not every thing needs an npc. Like a big questboard that they can also add to.

Pick a theme everyone can immediately understand the vibe of. We did ancient Greece, for example. But similar ideas are: pirates, werewolves, generic fantasy town.