Summer in Yellowstone is beautiful but crowded. I would look into some other famous waters, Beaverhead,big hole, Madison, Jefferson and ruby rivers are all in a short drive from Dillonor Twin Bridges, MT. I fished with an outfit called 4 Rivers http://www.4riversmontana.com/ . We had a great time; saw and fished some great country. They have accommodations at the fly shop but I would look into renting a house. Try something like this or easily search the web for more places.
http://www.vrbo.com/394951
http://www.vrbo.com/146251