Ok, that worked. Maybe it’s the links messing it all up. Let’s try again for a third time, without links…
Manti La Sal Wilderness is near Arches, as is of course Canyonlands. Just across the border in Colorado is Colorado National Monument which is worth a stop, as well as Rattlesnake Canyon which has a ton of arches on one easy hike on BLM land. There are many outfitters offering floats on that stretch of the Colorado River, since it seems they might be interested in that- the river is sedate thereabouts. Google “Grand Junction river outfitters”. Black Canyon of the Gunnison NP is within striking distance from Grand Junction- it’ll take just a few hours to stop by and look down from the rim, since going down into the canyon is quite the production. This could be skipped if it helps with the itinerary, though.
Then the choice is: north or south?
North means Grand Mesa, Flat Tops Wilderness, Glenwood Springs and it’s famous hot springs pool, and then the Aspen/Leadville/Breck/Vail region including Maroon Bells and other dayhikes. The stretch of I-70 east of Glenwood is a neat drive.
But I recommend south for a 10-year old.
South means the Durango and Silverton Narrow Gauge Railway (parking is free in Silverton but not so in Durango), Mesa Verde with climbing around cliff houses, Chimney Rock though it is new and thus somewhat mediocre, Pagosa Springs, a neat drive through the San Juan Mountains, Hooper hot springs pool, Great Sand Dunes National Park (which is an outstanding day destination for kids), Comanche National Grassland where you can hike or bike (drive?) to some dinosaur footprints, Bent’s Fort, and the Pikes Peak Cog Railway in Colorado Springs.
Bring a pail and shovel, a magnet, and a cheap plastic sled to Great Sand Dunes. There’s a great family-run Mexican buffet in Alamosa (Calvillo’s?). The Hooper pool is just a community pool that’s fed by a hot spring- so it is not the “experience” that Glenwood Springs is, but still a nice little pool. (My daughter always spends more time chasing minnows in the outlet stream than in the pool itself. When she catches them she feeds them to the ducks…) There is an RV campsite at the Hooper pool, too. I’ve never actually been to the pool in Pagosa.