We go to Breck every July (from Houston-sea level), travel with ages infants, toddlers, 5-7 year olds and teenagers, as well as 30’s thru 70’s. We have never experienced the altitude sickness that some do, but some do. Breck offers hiking, boating (Lake Dillon), white water rafting, basically all the amenities that the Colorado resort towns offer. Day trips to Aspen, Glenwood Springs, Vail, Leadville, Grand Lake, Estes Park, and Denver (maybe to take in a Rockies afternoon game). We can also drive it, we would have to fly to get to Tahoe. Both places are great for families.