The husband and I are currently kid-free, but we were in charge of a 4-year-old relative over a long weekend while his parents took a deserved vacation.
Since my husband is a kid at heart, we devised various activities for said kiddo to partake in. The highlight of our Saturday was a trip to Enchanted Castle in Lombard.
This place is like Chuck E Cheese on steroids. There's no ball pit, but there is a room's worth of climbing/tube-like structures, a huge amount of video games and ticket-producing games (skee-ball, Bozo's Grand Prize game, water gun races, basketball, etc., etc.), indoor bumper cars, indoor go-karts, laser tag, and a restaurant area with animatronic stage show.
Our little dude had a ball. He, loving the movie "Cars" and the video game "MarioKart" as he does, adored the go-karts. He also enjoyed the tube-climbing and the miniature bowling game, as well as just running around staring at everything.
One of the nice things about Enchanted Castle is that it offers things for a wide age range. Everyone from age 2-3 to older teens and even young-at-heart adults will find fun games and activities. And like Chuck E Cheese, it lets kids get some energy out in a fairly controlled environment.