L.S.
I don't have any cake ideas, but the Children's Farm in Palos Park is fantastic! I don't know about where you live in the city, but it is very close to the southside. They have all kids of animals, cows, horses, ducks, sheep, pigs, etc. That kids can get close to and pet. I've never been to a private party there (they do them), but we had a blast pumpkin picking and seeing the animals with my one year old this past October. http://www.palospark.org/center.htm#farm