J.E.
Phillips Park in Aurora is free!!! They have turkeys, ducks, otters, peacocks, Elk, a snake house, etc. Here is the link
http://www.aurora-il.org/ParksAndRecreation/MunicipalPark...
It is near the corner of Route 30 and Montgomery Road.
Since this is a park district (I think) you can bring a picnic lunch, and at the end of it all, there is a big, big, playground covered with Oak trees, which is completely shaded. You have to drive down to the next parking lot because it is a hike.
Enjoy!
J.