((I don't think this campground is alone with this kind of problem)). I have RV'ed for 30 years and not had a item stolen. Is there any other campgrounds that put some distance between you and the area? Like other's have said security cameras are only good after the fact and easily defeated with a hooded shirt. The only thing I could suggest is to lock everything up of a night, most are crimes of opportunity.
They do have motion detector flood lights and motion alarms that you could put up that might discourage thieves.