Approximately 30 minutes into the film the 4 year old, and two 6 year olds were ready to go. The dialog in the film sails over the heads of little guys, and they can't follow what is going on. Just too chaotic and slow moving. There are a bunch of action scenes, but they don't add much to the movie. The great animation and colors keep the kids attention off and on.
I liked this better than any of the comic movies, so far. Don't forget to sit through all the credits for the Avengers tease. I went with 10 people, and only 3 already knew anything about Iron Man. Everyone liked it. As every review has said, Robert Downey barely has to act as Tony Stark is basically Robert Downey anyway. There was one guy with us who hates RD and he still loved the movie. I have seen it twice, and will probably see it again. Great smart movie.