The DSM Farmers' Market on Court Ave runs 7am-12pm Saturday morning.
Visit the Iowa State Capitol (8am-5pm Friday; 8am-4pm Saturday) for a self-guided or pre-arranged tour.
Take a walk around Gray's Lake at Gray's Lake Park; if you are as lucky as Karen and Jeff you will spot the bald eagles.
Sample the pinball machines at Up-Down DSM Arcade Bar in the East Village (Friday before/after Welcome Dinner).
Grab a bite to eat at Fong's Pizza, Centro, or Big Grove Brewery (more recs available).
Find good coffee at Horizon Line (walk or drive) or Smokey Row (drive).