It totally depends on the kids. There is plenty of movement, color, music, dance, etc. to keep many young kids focused on the show.
My little guy has seen it twice, once at 18 months and once at 3 years and he was absolutely mesmerized both times. I don't think he ever took his eyes off the stage. I will say, though, that out of consideration to the other patrons who spent a lot of money on their tickets, I was ready to haul him out of there both times at the first little squeak. It never happened, though. He was fascinated.
It really is an absolutely incredible and breathtaking show. If you don't think your little one would enjoy it, I would reccomend maybe letting her enjoy one of the fun resort Kids Clubs while you take in the show. To me, it's a "DO NOT MISS" event.