Just as a head's up - Casa Bonita is not the place to go to eat. It's like a circus with screaming kids and families of 19 everywhere, the food is absolutely terrible, service is non-existent and it's a waste of time. The Garden of the Gods is really fun, and since you'll be in Co Springs go to the Cheyenne Mountain Zoo there instead of the Denver Zoo, it's much better, and you'll be near the Seven Falls. The Air Force Academy is kinda blah, I wouldn't bother.

You might want to go see the Butterfly Pavilion, that's something unusual that you don't see anywhere else. I've lived in Denver for 8 years and work downtown - you'll find plenty to occupy you on the 16th Street Mall.