Do you spend a lot of time at the Chicago Children's Museum? We do too.
We love this place. Our family membership is one of the best investments we make each year. When the weather is bad (as it so often is during the winter months), the CCM is one of my go-to destinations. My kids always, always have a good time. Plus, I can stop and get a Starbuck's in the Navy Pier Food Court on our way back to the car -- which is a nice way to cap off any play experience.
Have a look -- and please feel free to add your tips as well. I'd love to hear what your kids love about this place.