Before your trip, check on the approved generator hours for the campgrounds you'll be visiting.
At the North Rim you're at about 8,000 elevation and aren't likely to need AC (I was there a week ago). The TT got to about 80 inside mid-day, but cooled quickly as soon as the sun dropped below tree level.
At the South Rim you'll be lower and may benefit from A/C if your are OK to run a generator during the hours you think you'll be at the campground. Hopefully you're maximizing your time away from camp and enjoying the sights!