Check this out.....
http://www.citypass.com/chicago
You can buy a "City Pass" booklet and pay about 1/2 price for admission to.....
Shedd Aquarium
Skydeck Chicago
The Field Museum
John Hancock Observatory OR Museum of Science and Industry
Adler Planetarium OR Art Institute of Chicago
You have to use all the admission tickets within 9 days of when you begin using them. Most of the attractions have "City Pass" entrance gates where you don't have to wait in lines. It's a nice deal.
We have three children and we always stay in Chicago for a weekend before school starts. We like just 140km north near Milwaukee so we're being tourists in our own backyard but we love Chicago and we enjoy staying downtown.
The Art Institute is amazing.
Walking through Millennium Park near the Art Institute is great fun.
http://explorechicago.org/city/en/millennium.html
The outdoor concert area is designed remarkably well.....
You have to take some self portrait photos at the Cloud Gate with the city in the background......
Our kids love this art.........(we do too)......
I love Chicago. Have fun.