We have vacationed in Breckenridge (Summer and Winter) my entire life (I am 30 now) and we really enjoy it. There are some good restaurants, nothing too chainy, but do not expect NYC or Paris. Its a very walkable town with shopping, cafes, bakeries, tourist shops, etc...
From Breckenridge you can quickly get to Keystone, Copper Mountain, Frisco and Silverthorne. Each of the towns have their own unique vibe with Keystone and Breckenridge feeling like Breckenridge, Frisco being a resort town without a ski resort, and Silverthorne being the most developed in terms of shopping and entertainment (though I would never stay in Silverthorne, we usually go to a restaurant there called The Mint - Look it up, you all will like it, and the outlet malls which have some decent shopping).
Each of the towns have very good community websites with calendars listing upcoming events, this may help you in your decision.
Activities our crew does, with ages ranging from 1 to 63 include hiking, bike riding, cruising town, the alpine slide (look it up, its a blast), golf, cooking out, mining tour (outside of Breckenridge, a nice 2 hour activity).
Rentals in the entire area are very affordable during the summer month. We have outgrown our condo and now lease a large home when we all get together.
Hope some of this was helpful.