Keystone is sweet, still pretty reasonable in price but you're still right in the mix of all the other resorts which will give you plenty of options for activities. It's still somewhat of a local mountain which has kept the prices down. When i say keep the prices down i mean you can still get a good pizza for under $20, unlike Breck. If you guys will have a car, don't be afraid of staying a little further away from the resorts to save some cash.
"Government is the great fiction, through which everybody endeavors to live at the expense of everybody else." — Frédéric Bastiat