The Carnegie Science center was one of my fondest childhood memories, from going on weekends to the occasional summer camp.
At 20 years old, I went back with my younger sibling hoping it would be the same as it was when I was younger. Not to my surprise, the science center is aimed at a much, much younger audience and we both felt out of place. They have since removed the water exhibit on the fourth floor, one of my favorites.
Although overall it's aimed at a much younger crowd, the IMAX and submarine are sure to impress all ages. The IMAX is perhaps one of the best IMAX I've ever been in, with full surround video. It's absolutely surreal. The submarine tour is really fascinating and I would strongly recommend it to anyone who is able bodied.
The science center does have a foodcourt with lots of options, albeit it's very expensive as you'd typically expect from a museum setting. None the less, there's tons of seating inside and outside.
I'm not sure if they still offer them, but I took multiple summer camps which lasted all day for a week in the summer months. It was a great way for science geeks like myself to be exposed to more advanced technology that isn't available in normal schools. I took a criminal justice class which was really interesting.