There are so many options for campsites here. The description says 15 but I would guess there are hundreds of sites throughout this entire area, you just have to know where to find them. Granted, not all of them are as close to the bathrooms as one may hope.
Definitely bring some jugs of water with you. Most of the sites don't have quick access to water, however the Naches River makes for a good source. I believe recently they started charging per car for people staying at the sites, but it's worth it as they do have forest managers who devote their time to taking care of the area. Dirt bikers of the area tend to take over some sites, so if you are just going there to camp be prepared for the sound of dirt bikes throughout the day