First off, check out the various Epic passes by Vail resorts, the cheapest one, about $450, includes Keystone, A-basin, and Breck (with a few blackout days at breck).
2nd, have u looked at a map? cuz summit county, much less vail are all a trek and a half for you on any kind of day trip, which pretty much leaves you with Eldora which is pretty limited and not very in the mountains, or Loveland which is almost 2 hours from Greeley.
Not sure what kind of trips u plan to take, if its for big blocks of time then distance doesn't matter really.
Note most passes will go up in price by various increments throughout the season before they become unavailable.
is it late october yet?