I second the North Rim and Zion and Bryce along the way. To do this you'll need to stay over somewhere though-well worth the extra day.
QuoteCareful, though. This excursion takes you into polygamist country. Best be prepared for a possible run-in with polygamists.
Originally posted by: Don the Dentist
You may want to consider going to the North Rim, rather than the South Rim. Less crowded, better views (IMHO) and a more scenic drive.
Another idea is to stay overnight and hit Zion Park and Bryce Canyon the next day.