Is there much to do with the base admission fee? From the website, it looks like most of the cool stuff costs extra.

The base admission offer so much to see and do you will not be disappointed all the extra IMAX and Exhibits are just extras you'll be very pleased with the base admission especially if your first time there it's so overwhelming there is so much to see and do you will not be disappointed

Yes. There is so much to do that's included in admission. The science storm lab, the submarine, the eye-spy hall, and so much more