I saw the musical in Boston. I thought it was great. Nothing stood out as being inappropriate for a 9 year old in the musical--there were lots of children there. I have not read the book so I can't say much for the content of that and it's appropriateness. Have a great time! As a child I was obsessed with the Wizard of Oz and this seemed to really fill in some of the holes in the story.

Crisc