Ivy's on Clark, it's near Wrigley Field. It's the official gathering spot. I don't know if a minor can get in though.
Edit: Copy and pasted info from the ISUAA letter:
The Ivy on Clark sports bar & grill
3462 N. Clark Street (Clark & Newport Ave., about two blocks south of Wrigley Field). For the Iowa game, ISU fans have the option to pay $20 for unlimited Miller Lite drafts, well drinks, and wine for four hours starting at kickoff. That price also includes a $2 special on Bloody Marys.
CHICAGO - SUBURBS:
Fox and Hound English Pub and Grille
4320 E. New York Street, Aurora
(630) 236-9183
Fox and Hound Smokehouse and Tavern
1416 N. Roselle Road, Schaumburg
(847) 884-6821