There are plenty of short term rentals in Steamboat. We have a 4 BR place there that might work well for you. Here is our airbnb link. Let me know if interested and I can get you an Ag rate.
www.airbnb.com/h/snowinmyboots
Lots to do in the summer - hiking, fishing, mountain biking, float the river, hot springs (although it is summer). There are professional rodeos in the summer and frequent music festivals. Horseback riding. Alpine slide. Ice bumper boats at the skating rink. Also look at Steamboat Lake and Pearl Lake.