Wow, that sounds like an awesome trip for RVers!
For the Grand Canyon National Park
, you're probably going to be at the Grand Canyon South Rim
. That's the more popular area, and in September it starts to get trickier at the North Rim. Either way, you want to call ahead, campgrounds get booked way in advance.
You could check out Trailer Village RV Park
for full hook-ups. That may be the best option inside the park. Also see Mather Campground
, I think they may require a reservation in September.
Maybe also look into the North Rim Campground
if you don't need hook-ups.