You do not say how old the "kids" are, but I would take a stroller. It is quite a bit of walking. You do shuttle out to different places, but the stroller is helpful for while you are in the different buildings and walking around the "campus".
Also, there are places to eat, but just know that when I went to the food court area, I experienced sticker shock. It is expensive to run a space program, and they make sure to get their money where they can
Have a good time, you can spend as much time out there as you would like. I want to say we were there about 5 or 6 hours. Also, if you have boys and they are scouts, they can get a special badge for being out there.