The Museum of Science & Industry is worth a visit with young kids. They have the Ideas Factory with a special area for babies & toddlers - lots of padded foam shapes to crawl around, water & tunnels (like a small version of the children's museum). For older kids (under 12s) there is another hands on area with water & tons of interactive things to do. Other good things for kids there are the coal mine (complete with an underground train), watching chicks hatch from eggs and the train going from Chicago to Seattle. My 10 month old loves it.
Lincoln Park zoo is ok but nowhere near as good as Brookfield. The Peggy Notebart Nature Museum is also great for kids. You can sit and watch the butterflies - they may even land on you & they have lots of other hands on thing & some animals.
Enjoy the rest of the summer,
R.
I've heard that Lamb's Farm (you can google it) in Libertyville is worth a trip.