Don't Forget the Food!
Our favorite activities when visiting Chicago invariably include eating as much as possible. In particluar, you can get (of course) great pizza - my favorite is Gino's East which is pretty close to the Hancock Tower. Another great favorite is Italian Beef. Al's is on Ontario Street which is not as easy to get to without a car.
If you are going to go to the Hancock tower, you'll be on the Magnificent Mile which is a great walk.