For my money, I-70 between Glenwood Springs, CO and Golden, CO offers some of the finest alpine and subalpine views anywhere. I enjoy a soak at the Glenwood Hot Springs, notwithstanding the fact that it's a huge outdoor swimming pool--I just like it. There are plenty of places within NF lands to get a few miles away from I-70 for disbursed or campground camping. I like the side trip up to Tennessee Pass, almost to Leadville, in that it passes through Camp Hale, where the 10th Mountain Division trained during WWII. Veterans of the 10th returned home after WWII and pretty much established the recreational skiing industry in the US, particularly the West, where both Aspen and Park City skiing owes much to them.
South of Leadville, down Buena Vista and Salida way, there are more hot springs worth a visit. One can exit the Front Range down that way and re-connect with I-70 where it has slanted to the southeast at Limon, CO, and on to KC from there.
For your return trip, you have a golden opportunity to traverse the Nebraska Sandhills. Head up I-29 from KC, cross into NE via IA and NE-2 in the southwest corner of IA, run that up to Lincoln, then over to the Grand Island area about 90 miles west, and connect back to NE-2 west/northwest of Grand Island. You'll quickly enter the Sandhills and will stay in them nearly all the way to Alliance, NE. Along the way are developed NF campgrounds at Halsey and a remote but reportedly wonderful site up near the McKelvie Reservoir (Steer Creek CG). From anywhere along NE-2, north-south routes will bring you up towards the Badlands and the Black Hills.
Foy