If you are up for a hike - Eagle's peak is a trek but it's pretty awesome. It's a bit of a rite of passage for doolies (or it was) but if you love strenuous hikes with awesome views, it's the hike for you.
At USAFA itself, there isn't really that much. Not sure what's open to the public these days, but generally just driving around and looking at things is great. I'm not sure about USAFA tours this time of year - but maybe someone with knowledge or a cadet with some availability will chime in here. You can't get in to the cadet area very easily, so without a tour/escort you'll be limited to looking in at the cadet area from the chapel wall (assuming that's still open...I am realizing I don't even know what state of construction the chapel is at)