to entertain 2 kids in Chicago...?? (And 4 adults...including us!)

The plan is...
Arrive at a hotel around 2 on a Saturday afternoon; Saturday we can handle with swimming, eating, etc.

Sunday morning check out of the hotel, get some breakfast, then...?????????? We've done the zoo and Shedd's, and "no...I don't wanna' go to a museum!"

We have a 6 year old girl and an 10 year old boy to entertain for the day...home Sunday night, back to work for the adults and school for the kids on Monday.

Any suggestions????