We're going on vacation

Jack has been talking about Illinois for several months. Why Illinois? Because there is a Legoland there, why else? So over Spring break, we've arranged to make the trip to Chicago and have big fun at Legoland. I was able to book a suite (with a refrigerator, microwave, full breakfast and a POOL!) for about $107 a night. Who hoo!! The plan is to drive up on Sunday, swim for awhile, eat too much, go to Legoland on Monday (with buy one get one free coupons!), and play around some more. We're still looking for something to do on Tuesday. We were thinking about the zoo, but we're open for suggestions! So what fun things can we do in Chicago with 2 hoodlums?