What kind of camp is it? Will you be the only nurse there?
The absolute best book is called The Basics of Camp Nursing. You can buy it on Amazon
or through http://www.campnurse.org
. It's really invaluable. Other resources that might come in handy--a first aid guide and a drug book.
Always keep in mind that it ISN'T the hospital... kids are there to have fun and do activities, not rest in the health center. And it will probably not be a very clean environment compared to what you're used to... that's okay!
Those things may seem obvious, but when we have experienced RNs come to be camp nurses for the first time, those seem to be the two biggest problems they have.
Good luck! Camp nursing is a LOT of fun.