Since the wedding will be ending in mid afternoon, there will be plenty of time to hang out and catch up with friends and family in Oak Park/Chicago! Here are a couple of suggestions for things to do in the area, and Chicago is your oyster should you choose to be adventurous (the lake is gorgeous in late fall, if a little windy).
Family and friends who are staying Saturday night are welcome to grab dinner at one of the many great eateries in Oak Park, so feel free to do some research or explore when you get here!