But I'm not done in Utah yet, there is Capitol Reef NP, which while interesting isn't at the level of the others, but still worth a day if convenient, and Bryce Canyon and Zion near each other in the southwest portion. Bryce again is small, but very impressive and great hikes down to the bottom if you have the time. It's my wife's favorite. Zion is a bigger name and has lots to offer also but it can get very crowded in the summer, especially in the canyon where they have mandatory shuttles during the busy season. Bryce is higher elevation so not so warm even in the summer but Zion does get hot. In the same general neighborhood is Grand Canyon North Rim. Much different really than the South Rim, cooler, quieter and needs more work to really get into it. It does have a lot to offer, but you have to seek it out. Conspicuous perhaps by it's absence is Grand Canyon South Rim, which while enjoyable is almost a "can't get there from here" sort of thing from the Utah area. You obviously can, but it's on the order of 200 miles, one way, to get the 10 miles as the crow flies from one rim to the other.
The Utah parks, especially Arches and Bryce, are very accessible with minimal hiking required for lots of sightseeing. Hiking is rewarded if you like, but it's not necessary. And Zion, Bryce (plus GC North) have lodge complexes where many just relax rather than explore.
Here in my home state of California, Joshua Tree and Death Valley both have their points and I think Kings Canyon/Sequoia parks are vastly under rated. Everyone knows about Yosemite and even though it's kind of overrated, it's still a genuine "A" list park. Do go to extreme costs to avoid Yosemite Valley on the weekend though, it's just stupid crowded.
