I don't know when you are going.. but really consider seeing Gypsy.
I know, I know.. it might sound like an odd choice for kids, but I saw my first production at 9 or so and I was hooked! Mary Poppins, Mermaid, Lion King..etc. are shows that just rehash the movie material they have probably already gorged on already.
Show them something that will stay with them and evolve with them throughout there lives. I submit this qoute from the Frank Rich 1989 revivial review:
'Gypsy' may be the only great Broadway musical that follows its audience through life's rough familial passages. A wrenching fable about a tyrannical stage mother and the daughters she both champions and cripples - yet also a showcase for one classic Jule Styne-Stephen Sondheim song and rousing Jerome Robbins vaudeville routine after another - 'Gypsy' is nothing if not Broadway's own brassy, unlikely answer to 'King Lear.' It speaks to you one way when you are a child, then chases after you to say something else when you've grown up.
Give it a chance.
What great ones do the less will prattle of