Noob trekking from Kalispell to Yellowstone to Mt Rushmore

Since you're not in a hurry, I'll throw out another item along the route for consideration.

There are a number of Forest Service Campgrounds in the Bighorns along routes 16 and 14. The only one we have stayed at was Tie Flume on route 14, but if the others are as nice I'd highly recommend. Also if you take 14 across, stop at Shell Falls on the way up the west side.