It's my 3-year-old son's favorite restaurant, hands down. He requests it because he loves eating in the cars.
And to be honest, I'm not sure how much he really pays attention to the movies (though they have never scared him... and this is a kid who refuses to ride Winnie the Pooh b/c there's 3 seconds of thunder at one point). He seems to watch the cartoon clips and loses interest in some of the older sci-fi movie ones.
I think if a clip comes on that they find scary (which would be few and far between), there's enough stuff to distract them until it's over. They get a kids menu/coloring page with crayons, there's other cars to look at, food to eat, etc.