Chicago is big. There are cars, trains, taxis, pigeons, people, and huge, tall, massive buildings.
Let's face it: Wandering around and in the shadows of all of these things can get pretty boring. Most kids don't like shopping or architectural tours or eating at fancy restaurants. Most kid's just want to - well - do kid stuff.
For the young ones of the group, there is the Kohl Children's Museum in Chicago's north suburbs. I used to go to this museum as a child, and while people told me I did other 'Chicago' things, I only remember this Children's museum. It doubles as an interactive learning center and is incredibly hands-on.
Older kids might enjoy the Adler Planetarium or the Shedd Aquarium, both of which are located within walking distance of one another. The Planetarium is a museum about space, stars, planets, and the universe. The Aquarium, on the other hand, is about the universe under the sea, and has exhibits dedicated to creatures you might never have known existed.
Kids (and adults) of all ages will also enjoy the area surrounding Millennium Park. There you have 'Cloud Gate,' the giant reflective bean (what's not to like about that?) and the Crown Fountain, which is comprised of two forty-foot towers with LCD screams and waterfalls and spouts running during the warm months.
As for food for the kids - that might be the easy part. Pizzeria Unos offers authentic Chicago-style food, which should be introduced to all people at a young age. There is also the Rock 'N Roll McDonalds in River North, which is a required stop, even if it's a little gauche. When has a kid ever complained about something being gauche?