We did go in LA. The kids enjoyed it, but were not overwhelmed. First, prepare them for the fact that the big mask is not there, even though it is on the program, bags, advertisements, souvenirs, etc.
We would have enjoyed it more if it weren't so crowded. My DD8 had a hard time getting close enough to the items to get a good look. She definitely could not get close enough to read about anything. The audio tour was a lifesaver. Thus, my recommendation is to go on a weekday, not a weekend.
We checked some books out of the library prior to going and there were many items that were pictured or described in the book, which were very fun for them to find in the exhibit.
Finally, Tut is only the last few rooms. The beginning of the tour is other Egyptian items.
The crowd and long lines made it hard for the little ones, but it was worth seeing. You can spend as long as you like in any given area, and I don't see why you couldn't go back, at least before you exited into the gift shop, you'd just be swimming upstream.
