Moab: hiked the the delicate arch (our kids are 7/9 at the time they did it no worries)
Durnago: stayed in Purgatory, really cool kids stuff, zip line, alpine slide, also short amazing day trips.
Mesa Verde: WOW, middle of nowhere, but holy crap amazing, my kids loved it
Great Sand Dunes National Park: cool area, rent sand toboggan
Four Corners: didn't think it was worth it, went becuase our family from the states wanted to stand in 4 states at once, it is in the middle of nowhere.