My experience has been that I go through less food than normal due to the on-site vendors. It's just easier to grab something on the go, than walk all the way back to camp and make every meal there. This may not be as big of a deal for people who are there on day passes, since their schedules have more flexibility. We usually camp with friends, so we've been known to do some spur of the moment group happy hour/dinners. Probably want to consider that possibility & discuss it with friends you are planning on meeting / camping with.
I go through more drinking water than normal. It's hot, the days are long, and the drinks around the campfire at night are more plentiful than normal. Water is your friend.
Add a hat & sunscreen if you don't normally take/use them.
I never find time for "recreation" (mountain bike rides, hiking, etc). If it weren't for the long trips between the staff building & the areas I typically work, I wouldn't bother with bringing the mountain bike. If you have specific plans to ride/hike/etc, you may want to bring that stuff - but if it's more of a "just in case I feel like it" kind of thing - I'd say leave it at home.
Shade can be hard to find in the camp area - if you spend a lot of time there, you'll probably want to bring your own. Just be sure to do a good job of securing it to the ground (or side of your vehicle, etc). A couple years ago a vendors easy-up took a flight (despite being secured to the ground) & did some damage when it came back down (punched a hole in someones camper & hit a couple people). Even on calm days, strong gusts of wind come through.
If you bring a dog - be sure to have a way to keep them cool & plan to let them rest somewhere quiet. There is a lot going on (even in camp), & my experience is that they can easily get over stimulated & start acting like a toddler that missed his nap. I don't take my dog any more because of it. Also don't let your dog off leash - even if its the friendliest dog on the planet. Last year there was a fight between a less than friendly dog that was on-leash & a very friendly dog that was off leash. The guy with the on-leash dog couldn't get the other guys dog away from his. It was a bad deal for everyone. If you want to exercise your dog off leash - plan on taking them off site to do it. For some people (roof top tent users, etc), that means breaking down camp & finding an escape path through the camp site - so plan your camp site accordingly.
This isn't a "trip" per-Se. Once you are on site, you probably won't use your vehicle much, if at all. If you're not in any of the driving classes, or leaving the site, you likely won't even start your engine the whole weekend. Be sure you have the power to run what ever it is you need to run (fridge, lights, etc). The days can go by fast & running engines / generators at night isn't allowed. So if you're planning on charging your batteries off of the alternator or generator, be sure to leave time in the day for that. This is especially important if you plan on going to one of Paul May's parties - not much chance of getting back to camp in time to charge up before the noise rules go into effect.
Over all though - just your normal camping stuff.
