This week is Colorado Craft Beer Week, so there will be some cool beer events/tappings around town this weekend. If they really want to experience Denver, I would recommend walking around downtown Denver and stopping by a few breweries/brewpubs.
On Friday, Falling Rock Tap House (one of the best beer bars in America located right next to Coors Field) is holding a Sour Fest, where they will be tapping all kinds of delicious rare sour beers. From there, I would recommend that they walk down Blake Street past Coors Field and visit some of the new breweries in the RiNo neighborhood. I would recommend River North, Ratio Beerworks, Beryl's, Black Shirt, Crooked Stave, and Epic, which are all located within a few blocks of each other just north of Coors Field. Black Shirt Brewing is doing special beer tappings and hosting live music in their tap room on Friday night. If your son's lady friend is into wine, they could also check out the Infinite Monkey Theorem winery in that same part of town. Also, right in that same area on Friday night, there is a Friday Night Bazaar where they have live music, food trucks, booze, and various local vendors. I haven't been to the Friday Night Bazaar yet, but I have heard good things from my friends who have been before.
On Saturday, I think I am going to check out a bluegrass concert at the 1Up by the Denver Bluegrass Generals, which is composed of two guys from the Infamous Stringdusters and Sam Bush -- two of the headliners from the Winter Wondergrass bluegrass festival that I went to last month. They both put on a great show for the festival, so I am sure that this composite bluegrass band will put on a great performance as well. The 1Up is a cool place to see a show as well, as it has tons of old school arcade games (PacMan, Mario Bros., Mortal Kombat, Donkey Kong, etc.), ski ball, and pinball games.
Some places that I like to eat around downtown include Freshcraft, Work and Class, Denver Biscuit Company, Torta Grill, Kitchen Table Cafe, Snooze, Biker Jim's, Lucky Pie, Illegal Pete's, Euclid Hall, and Cart-Driver.