we drove an hour and a half each way to stand an hour in the half in the San Antonio TX heat w/ 2 kids w/ autism spectrum disorder. Was it a huge challenge? You betcha. Was it worth it? To us, absolutely. It was something we wouldn't be able to do again, the kids loved the interactive stuff, they really enjoyed learning about the movie and how it was made, they loved the sneak peek in 3d at the end; it was great all around! Then we went for a special lunch, so it really was a great family day out.
Honestly, I think a lot of it depends on your attitude towards it. If you think it's just a display, and not worth the wait- it won't be worth the wait, and your kids will follow your example and not "get into it"
But, if you go into it with a really positive attitude, and talk about it, and make it special for them- then it will be.
My kids have talked about it since and how fun it was; and the free paper pieces we got to make ornaments were put away until after we see the movie, so they'll get more family time out of it too.
Personally, if your son likes trains, movies, computers or learning how things are made- I'd definitely take him; but I would encourage you to go right at the beginning, so the lines aren't too long.