city of rocks,
Camping when I went down was easy, just pull in on a weekday, and keep the spot as long as you want (i can't remember the fee's thougth, sorry)
The only think to be aware of for the kiddy, is that the granite there is REALLY sharp, and eats finger tips like nothing I'd been on before.
There are lots of great bumbly routes, it is still one of the best trips I've ever been a part of... And the scenery (if you like rocks) is so astonishing. Take a camera...
Go for it!!!