Lived in Denver for a year.
Here are some suggestions:
1) Go west and drive up into the mountains. They are the single most impressive thing in the Area. Loveland Pass/Continential Divide is cool. You can see a highway about a half mile out in front of you and 2 miles down, and its pretty freaky!
2) Once in that area pretty much go any direction and find a skiing place. Go skiing or snowboarding.
3) Come back sore and cold into a small town near the ski resort. Hang out with locals and ski bunnies.
4) Go back into town and get stopped at DUI checkpoints. I know you don't like bar/club scene but be prepared to be stopped anyways.
5) If you just want to hang out in a "hopping" area with bars (even if you dont go there theres other stuff aroudn) there is 18th street mall. Which is right on the outskirts of downtown (on 18th street north east a bit of downtown check internet), but lots of college girls in that area to drool over and its the "hang out" area...
I can't suggest much more. There isn't much more to Denver except nightlife/bars from what I remember. Downtown is ok to roam around, there are some cool parks and nice areas to just walk around, but there is a huge gay community and a ton of beggers if that bothers you. Things don't become rough (hoodlems) until a bit out of downtown a few miles provided you avoid Colfax avenue.
Denver is pretty boring. Its the mountains and things associated with it which is the attraction. Be it skiing/snowboarding in winter, or rafting, fishing in the summer.