Wow, thanks Donna and Southwest Dave.
I'm under the impression that from St. Louis to Denver is approximately 12-13 hours. Since I like lots of stops and stretch breaks with food (lol) I'm thinking between both my daughter and I driving it can be done with no problem. I've done worse to the east coast before.
But I haven't driven this route before so I'm unfamiliar with it. So I appreciate your advice and will take it to heed. I'll monitor it as we go.