M.M.
You've already got some great suggestions for the actual farm atmosphere. However, if you were thinking of within city limits, the Chicago Park District (http://www.chicagoparkdistrict.com/) hosts Pumpkin Patch events at various park locations - an urban pumpkin patch experience. They often have a petting zoo, prepicked pumpkins set out for kids to choose, various activities. In no way is it like some of the places already mentioned but just another option. I don't know where you live but there's one on Sat, Oct 17 from 11 a.m. to 2 p.m. at Kenwood Park in the Hyde Park/Kenwood area.