I've done the White Rim Trail twice, once each direction, with my daughter on our Chinese bikes. Great scenery and not a difficult ride except for deep sand on the west side. It was hot, nearly 100 degrees and there isn't much shade.
Don't forget to stop at Mussleman Arch for a pic.
A ride up to the top of the LaSalle Mtns is a good way to escape the heat and the aspens are real nice in the fall. This was at the end of September.