What’s an easy fun route

I think cutting over through the southern part of Utah and Colorado via 160 in Colorado is the best.  I'm a national park buff, Zion National Park and Mesa Verde National Park are on the way. You may need to make reservations depending on time of year and park. There's also Four Corners Monument which is a man made landmark.
If you go a touch further south you could hit the north rim of the Grand Canyon National Park. Canyon de Chelly National Monument into Monument Valley all beautiful spots. Pagosa Springs (Colorado) is a neat spot. Multiple hot springs to relax your muscles.
It's an incredible part of the country going from dry canyon lands to the lush evergreens of the Rockies. One last stop my favorite place in Colorado, Great Sand Dunes National Park and Preserve. Oh just south of Alamosa is Jack Dempsey Birthplace, safe and fruitful travels.