If you must stay in Des Moines, I agree with previous poster to hit Court over Racoon River. If you have a little more time and transportaion, Olde Main in Ames is better yet. And though i've not been there, if you can squeeze extra time, Peace Tree Brewing in Knoxville is supposed to be quite fun. Their a small Micro Brewery that use theri 4-5 typical brews on tap, but they do alot of experime4ntation, and these experiments are on tap in their tap room. They don't sertve food, but allow you to bring food in from town restaurants, and I here many local restaurants will deliver to the tap room,,,,,,,,, Now I want to go down there this weekend ;-)
Another non-microbrewery (downtlown in same area as Court) is the Hessan House. Alot of German beers and german inspired food.