A possibility to avoid some of the interstate and see some of the local areas is: take I70 to Topeka, KS, north on US 75 to US 36, west on US 36 to US 83. North on US 83 to North Platte, NE. The Holiday RV Park in North Platte is an easy in, easy out park that is nice. West on I80 to catch US 26 west toward Scottsbluff and then over to I25. North on I25 to I90 and then west. This route has lots of interesting places that are worthy of a stop but the roads are such that you can make decent time. It also goes by a couple of the places you specifically wanted to visit. We have done this route several times on our way to Montana. Another possibility is to stay on I70 to US 83, but you miss some interesting spots this way.