Red Rocks is in Morrison, so Dinosaur Ridge is worth seeing if you want to check out fossilized dino footprints. I saw them nearly 25 years ago and still distinctly remember what they look like, they left that much of an impression on me. The Denver Art Museum is pretty nice. The Natural History Museum (or whatever they call it these days) and the Denver Zoo are collocated and both worth seeing, and they're basically downtown so you can visit 16th street mall or the capitol afterwards. If you're downtown, D'Corazon Mexican Restaurant is really good. I'd recommend going to Twist and Shout Records if you're into indy, rock, classical, or metal music, but if you're mainly into electronic music it's not worth the trip. Denver's music scene is huge, so there might be concerts worth seeing besides Shpongle. Check listings for Ogdon Theater, Blue Bird Theater, Mammoth Event Center (nm, it closed). There might be new venues in addition to these, but these were the best back in the day.
If you're into the outdoors, I'd strongly recommend getting up into the mountains. Clear Creek Canyon is nearby and worth exploring. Mount Evans, one Colorado's 14kft peaks, is an hour and a half away and can be driven up (the highest paved road in North America). It's totally worth doing if you've never been up a mountain that high. Lots of the mountain stuff I like doing is up north closer to Boulder (Flatirons, El Dorado Canyon, Rocky Mountain National Park, etc) which is a few hours away through dense traffic.
After reading my recommendations, I realize that I'm officially in "dad" status. I don't know any clubs or bars because I moved away when I was 19.