I just saw United 93 and it gave me a headache. The first 15 minutes are very slow chatty stuff to show what a normal morning it was - I'd recommend going in 15 minutes late. There's a lot of other slow stuff to fill time. Then you're on a doomed plane. The camera angles are weird through the whole thing and made me a little dizzy. So in short, don't bring the kids. Except that some of the money is going to WTC charities so I guess I should encourage that part.