You could always go stay in the Yellowstone/ Grand Teton area. Lots of good fishing around there and only a couple hours more down the road. Many river around there just outside the parks hold lots of fish and have a lot less pressure than the parks(i.e. Wind River in WY) . Then again the rivers in that Parks are really good fishing. Try the Snake, Madison, Yellowstone, Firehole, etc. The parks are also alot of fun witht he kids, seeing the mountains, lakes, rivers, animals, gyesers, etc.