It is a wonderful story, beautifully animated and full of imagination. I recommend it for tweens and up. I watched this film with my child and two other kids in a theatre and I thought it was wonderful. There are some sad scenes that may scare some children. My kid was 7 years old when we saw it and didn't like those scenes, but the older children (of 9 and 10) were ok with them.
I liked the strong lessons about tolerance. Watch it with your younger kids and explain what they may not understand.