I guess it really all depends on how you want to do your trip. You're likely looking at about 3, maybe 4 days of hard driving if you're planning to drive straight there. The variable will be how well the kids hold up. If your 6yo is anything like my son, he'll be easily entertained watching movies or playing with a handheld game. The 11mo, will likely be a challenge. Your wife may not like you too much she has to sit in back trying to sooth the baby because they're cranky.
I can probably tell you your first day to day and a half will be spent getting across IN, IL, IA and NE. Long, boring and far from scenic. The repetition of corn, soy and cows becomes monotonous. If luck is on your side, you'll be able to get to Omaha, if not hopefully Des Moines. Other than that be mindful of your gas as you're heading out of CO into UT. If memory serves me right gas stations were few along 70.
If you have the time on the way out, maybe fit in a stop off to Bryce or Zion Canyon in Southwestern UT.
What else can I tell you...
As far as places to stop at or see, unfortunately in the trips we've made out there, we've been road warriors just trying to make it to our destination stopping primarily for gas, rest room or to eat. This year we learned the "joys" of traveling with an infant. Let me just say, may the force be with you.