Too bad, it's expired. But you can still get a family membership there and it's not a bad deal, and it's gotten us into lots of expensive museums in other cities for free. Worth it at full price too.
The Notebaert Nature Museum had a Groupon for two days for a thirty dollar family membership- good for a whole year. It's for new members only :( but a good deal if you have wanted to join and haven't.
Good for two adults and all kids in household and care givers. Not sure what the guest kid policy is there...we couldn't really tell from the description. Worth a look anyway! Check it on the Chainlink link on the lower right side of our page!