If you can find a little extra time please check this out on the way to Glacier National Park:
http://www.ridethehiawatha.com/
This place was a gem we found when going from Glacier NP to Coeur d'alene (about 5 miles east of Idaho/Montana border. If you do have your bikes, I recommend going north to south for the steady downhill direction (and arrange for a shuttle return) otherwise the northern direction is all UPHILL. If you don't have bikes, then much of it can be driven. I wouldn't recommend you do this with the rig - unhitch first. There are bunches and bunches of tunnels and tressles in an attempt to build this train route. The train route has been gone for some time and now it's been converted to biking and driving trails and roads. The scenery through here is AWESOME (we also saw moose and lots of deer from a distance, too).