A.R.
I suggest Stade Dairy Farm as well, and we went to Boo at the Zoo last year too. Don't forget to check your local library and see if they are having a special program or festival.
Also, if you get a chance, pick up a Chicago Parent magazine, or visit them online: www.chicagoparent.com
I recently relocated here myself and I have found LOTS of information about events in Chicago Parent. They even have decent articles most of the time!
Have fun!
-Amanda