Hi, thanks for chiming in, but the thread is about 13 years old. Chances are, that trip is over and done with already.
You did hit the nail on the head, though ... an RV rental isn't cheap, but it is great fun. It's a lifestyle/travel style rather than a way to save money. Unless, of course, you happen to need 2 or 3 hotel rooms every night to manage your group! I've seen folks rent a good sized motorhome AND get a small tent ... the kids sleep outside in the tent. Most campgrounds seem okay with that, too.