Manitou Cliff Dwellings is not too far from the Pikes Peak entrance and has been owned privately for many years. It is not quite as archeologically original as Mesa Verde because many of the walls and ceilings have been covered with cement to stabilize them, but they do allow you to enter the dwellings and walk around, which is good for kids.
The kids were able to walk behind the front walls into some of the interior spaces. This photo shows a kiva you could look into.
Sticking your head out a window seemed to be a favorite pastime.
And here you could climb a ladder and then into a window to see some of the small sleeping rooms. The kids had a good time on the balcony.
There was even a teepee kids could go into.
One of my favorite state park campgrounds in Colorado is Cheyenne Mountain State Park. The big mountain in the background is the once-secret nuclear-bomb-proof installation that was supposed to save us in case of a nuclear attack during the cold war. It is still used today, but considering that the entrances are well-lit and well-marked, it is not much of a secret anymore. Nice place to camp, in any case! I had myself, two other adults and three kids in my motorhome.
And, right next door was my son's trailer where his family, including two other grandchildren stayed.
Some'Mores were popular.