There is a fair amount to do, but the weather can be quite unpredictable in December in KC (I lived there in the 80's). Basically, prepare for an ice storm, and be thrilled if the weather is actually better than that, which is how the locals live. There are plenty of indoor activities, especially such as Crown Center and around the downtown area (shops, restaurants, theaters, etc.), and of course KC has long had a very lively jazz scene all over town. Don't miss Arthur Bryant's BBQ, or Haywood's, which is not as legendary but possibly even better. Public transport consists of not-great buses, so try to cluster your sightseeing (downtown, Westport, Plaza, Crown Center, etc.). Both the Plaza and Crown Center have great holiday displays, but be prepared for a massive crush of people.