Driving from San Francisco to Denver Colorado... with scenic stops?

I would suggest renting a car because if it breaks down the rental company will fix it or replace it. But, a lot of rental companies don't rent cars to people under 25, and either way the driver has to have a U.S. driver's license. They should see Las Vegas, the Grand Canyon, and Bryce Canyon. In Colorado they should go to the Manitou Springs area and see the Garden of the Gods, Pike's Peak, and go horseback riding. Denver's Museum of Natural History is cool. I hope they have a great time!