Think you will enjoy the US 2 routing better, even though on the west side it's kind of curvy in several places; just don't travel it on the weekend. Both routes suggested above have you going through Spokane, US 2 in Spokane is really slow and lots of stop lights. Try to travel it in mid day or better yet on Sunday. Once you get north of Spokane, the route is good and you will enjoy the scenery; Newport, Priest River, Sandpoint, Bonners Ferry, Troy, Libby are all nice towns and no problem on driving through them. Have a good trip!