Sure, my two daughters (ages 5 and 9) were impressed with the Grand Canyon. But what they really enjoyed during our recent Arizona trip was our visit to Bearizona, a wildlife park in Williams, AZ, about an hour south of the South Rim of the Grand Canyon. Bearizona is a drive-thru zoo--think Jurassic Park but with living mammals instead of extinct dinosaurs. No one was eaten on our trip there, but there's nothing stopping the black bears and tundra wolves in the park from coming right up to your car as you drive through. Visitors are instructed to keep their windows rolled up while in these enclosures, and to drive slowly away if one of these potentially dangerous creatures approaches their car.
We didn't have to worry about such things during our visit, since the bears and wolves were lounging about trying to stay cool in the summer heat. The bison were more active, with the entire herd crossing the road right in front of us at one point. One of them even sniffed around the front of our car. Also on view were big horn sheep, mountain goats, and, in the walking part of the zoo, beavers, foxes, and baby bears. I can now attest that baby bears are just about the cutest things ever.
If you're visiting the South Rim and have kids, be sure to work in a couple hours at Bearizona. It's well worth the time.