I am planning family trip with my 11year old children to Colorado this summer. We will want to see a Rockies game for sure - where else should we go? We have about 12 days including travel to/from new jersey - thanks for ideas!!

So this means your driving or flying? What month?

Rocky Mnt National Park (2-3 days)
Great Sand Dune National Park (1 day)
Mesa Verde National Park (2 days)
Durango (1-2 days)-if budget allows do the zipline/train ride
www.soaringcolorado.com
Black Canyon of the Gunnison National Park(1 day)

Perhaps Colorado Springs, Pikes Peak


Alpine Slide at any of the ski resorts
I think Winterpark has one. Other places do also, but I can't remember where all we have done them at. Perhaps at Vail or Keystone.

Perhaps rafting somewhere.

I would not try to do the whole state. Stay in one area & enjoy it. South, Central or north, lots to do. You decide what you want. Many can help you here but perhaps you should get a travel guide & look at the various areas first.

Colorado is a good state to travel around.
At 11 I really suggest the dinosaur museum at Woodland Park, just outside Colorado Springs. Then there is good bit around there==the Air Force Academy, Garden of the Gods, etc.
That is just south of Denver. Maybe head to the mountains--Leadville, and one of the Alpine slides. Then perhaps head up toward the Rocky Mountain national Park through the western side, and then back down to Denver.
I think western Colorado might stretch the trip a bit.

Denver also has a nice zoo, if you don't have one in your home town.

To add to Gretchen's ideas- Take a tour of the state Capitol building and maybe the Denver Mint.
I usually travel through Colorado on Amtrak. Take the train from Denver to Glenwood Springs. There is a good bus system from Glenwood Springs to Aspen.
The largest hot spring fed swimming pool is within walking distance of the Amtrak station in Glenwood Springs.
The kids would love a train ride through the Glenwood Canyon.

Go to your local library or buy a guidebook for Colorado. You question is so vague that it is difficult to answer in a meaning way. Really needs some background information as to likes, dislikes, etc. Think how you would answer if someone asked you the same question of New Jersey.