IMHO
With the kids in mind St Louis 2 nights spend a day exploring the
Arch
Overnighter in Topeka
Another overnighter in Dodge City with some cool Cowboy tourist things for the kids.
I would skip RMNP your going to see some GREAT Rocky Mountain Scenery going across Southern Colorado
Stop at Brents Old Fort on the way to Great Sand Dunes (from Dodge City to Brents you will be following the old Santa Fe Trail)
Your times from Great Sand Dunes to Las Vegas are good
Cut back a day at Yosemite
Cut back a day at Crater Lake NP and find you a overnighter half way on the way to North Cascades NP
Cut back a day at North Cascades NP and find you a overnighter half way on the way to Glacier NP
Cut back a day at Glacier NP and find you a overnighter half way on the way to Yellowstone NP
Just overnight at Devils Tower three hours is enough time at Devils Tower the next morning before heading out. Teddy Roosevelt NP
IMHO Mackinaw, MI is so close to home you can go there easily from home so here is what I would recommend after leaving Devils Tower.
Spend 3 night in Deadwood SD at Whistlers Gulch and Gulches of Fun amusement park is right next to it. Spend a down day you and the DW let the kids play all day. Then spend a day at Mount Rushmore, Crazy Horse and the Mastodon Sight. Then have at least two overnighters on the way back to Cincinnati, OH
