This is such a great place to take young children to. Amazing activities and learning around every corner. The best thing to do is to walk in and let your kids be themselves. Let them play in the grocery store they way they want to (while respectful of others), or create their own contraption on the magnetic walls. I love seeing my son and his cousins explore and create in all the rooms.
The best deal is to get a membership. With so many ways to play and learn, the museum offers endless options for kids. My son has never been bored regardless of how many times we've gone.