If you're able to get to the Moyie it's definitely one of the most beautiful and fun rivers you'll ever run. Class III boogie water for lots of it and the forest is gorgeous. And you get to go through a breached dam as well. It's waaaay up in the northern part of the state but well worth it if you can get there. Also if you're in that area, the Kootenai is a pleasant, easy float (well, except for the falls...) with easy access, at least near Libby MT but probably down a lot of its length.
Have a great trip!
Nothing in the world is more yielding and gentle than water. Yet it has no equal for conquering the resistant and tough. The flexible can overcome the unbending; the soft can overcome the hard. - Lao Tse