Joseph:
Per Illinois law:
“…the possession and dispensation of wine by an authorized representative of any church for the purpose of conducting any bona fide rite or religious ceremony conducted by such church shall not be prohibited by this Act.”
Purim is not a rite or ceremony, and even if it were, any such liquor would have to come from an authorized representative. Provide liquor to minors on purim at your own risk.
Additionally, even if you CAN fit it into an exemption, if that child does something c”v, you will most likely be liable. Think about that before you start pouring.