Fair warning: free days can be BUSY! I believe Chicago Public Schools on a traditional schedule get out June 19th, so you might consider going before then. Please visit each website to double check dates.
Adler Planetarium
Free June 3, 4, 5, 10, 11, 12
Art Institute of Chicago
Free every Thursday from 5-8pm
Children under 14 are always free.
Lincoln Park Zoo
Always Free!
Chicago Children’s Museum at Navy Pier
Free for everyone – Every Thursday evening, 5-8pm
Free for ages 15 and under – First Sunday of every month
DuSable Museum of African American History in Hyde Park
Free on Sundays
Field Museum of Natural History
Free June 4, 5, 9
Museum of Science & Industry in Hyde Park
Free June 1 - 6
National Museum of Mexican Art in Pilsen
Always free!
The Oriental Institute in Hyde Park
Always free!
Peggy Notebaert Nature Museum in Lincoln Park
Free on Thursdays
Shedd Aquarium
Free June 2, 3, 9, 10, 16, 17
Garfield Park Conservatory
Always free!
And last, but not least:
Millennium Park concerts - Ms. Vietzen's favorite thing about Chicago, you might see her there!
Free concerts several nights a week, so bring a picnic. (I think this is a great way to expose children to music and concert-going without splurging on an expensive ticket.) The green and blue lines will get you close, and, if you can keep a secret, parking in the Aon building is a good deal if you're in between 3pm and 6pm.