There are 32 dude ranches registered with the Colorado Dude Ranch and Guest Association. The majority of these are spread out all over the state, with the three closest to Denver being Peaceful Valley Ranch, North Fork Ranch, and Lost Valley Ranch.
Dude ranches offer a unique approach to vacationing, wild west style. Oftentimes ranches have programs in place for you and/or your children to participate in either together or separately, in addition to having activities available ala carte. Horseback riding including trail rides, overnight pack trips, and more, are a standard activity at a dude ranch. Other options you will be able to participate in include activities with cattle, hiking trails, fishing, fly-fishing, swimming, campfires, hay rides, cookouts, horseshoes, overnight pack trips, evening entertainment including cowboy poetry, music, dancing and more, river rafting, four-wheel drive trips, tourist trips, mountain biking, tennis, golf, rock climbing, kayaking, shooting sports, and more.
Sources:
http://hotel-guides.us
http://accommodations.orbitz.com
http://www.denver.org
http://www.bbonline.com
http://www.coloradodirectory.com
http://www.coloradoranch.com