Hey Andrew,
Rocky Mt NP sounds like a great idea. I realize that Colorado is actually West of where you are interested in going, but I am not sure what you can do in a one day drive from Kansas. I would say that Tennesee would potentially be a phenominal place to go visit at that time of year...though my guess is that the leaves are turning a bit later than that...and I am not sure if you could actually drive it in a day or so.
Curiously, what do you consider a 1 day drive to be? I think even Rocky Mt. National Park may be a two day drive (depending on where in Kansas you are from).
James