As a flatlander who went to Breck this spring, the elevation hit me hard. Not sure if staying in Denver for a day or two before might help but we had to pay a visit to one of the oxygen bars first day there.
It would help some, but Breck is @9500 ft, so it is still a big jump from Denver. Altitude sickness is no joke. Upside, 1 drink will go farther...