Colorado Mt suggestions
 

Wife and I are using frequent flyer miles to Denver later this month and would like a 3 or 4 day trip to a nearby mountain area. We've been to Aspen, Breckenridge, Vail, etc., which are great, but for a short trip, we would prefer a lower elevation since the altitude bothers us for the first several days. Any suggestions for a place within a few hours of Denver that offers nice scenery, but less elevation than Vail, etc.?

Estes Park, the gateway to Rocky Mtn Nat Park, is at only 7,500 feet in town, lower than all the others you mentioned. It's only an easy 1 hour 15 min drive from DIA and August is a great time to visit this area. A couple of days in the park offers fantastic scenery, opportunity to find trails to hike that meet your ability and, of course, relax!

Exactly. RMNP would be a perfect place for your vacation!!

I agree with Estes and RMNP. But how about the mountain village of Evergreen, home to some beautiful B&B's, good restaurants, hiking, fishing, and a short drive up to the top of Mount Evans, which boasts the highest paved road in the nation? Evergreen is an hour's drive from the airport and is right around 8K feet or so.

I would recommend Colorado Springs - it's closer and it's lower (6200-6300 ft). Tons of stuff to do and see.

Another vote for RMNP. But if 7,500 is too high, the CS would be OK, too. (Though not exactly "mountain towny.")

If altitude is truly an issue, may I suggest spending one night in Denver before heading up into RMNP? If you haven't been to the park, it is truly awe inspiring and I'd hate for you to miss it b/c you spent the entire trip sick in your cabin/room! There's enough to do in town keep you busy for the day and the night's sleep at only 5,280 should make the transition easier.