This is one of the only play areas in Chicago that is open on the weekends - most of the others close for birthday parties. It's clean, new, friendly staff, great for kids up to about age 6. The only negative is that parking is terrible and expensive. If you find a meter you have to run out and plug it every 2 hours. If you can, take the bus or the train!
Kids are $15 for the first kid, then $11 for other kids, parents are free.