I wrote a storybook for my first grandchild called My Two Grandmas and illustrated it with altered photos. She is lucky enough to have two grandmothers living close to her. She loved the little book, and then I had to make one for the other Grandma too!
I'm working on a big novel for children - sort of 9-12 age range. It's very difficult to pitch it just right, and I find myself having to rewrite big chunks because I've just gone into way too much detail - you've got to keep a child interested, and it's easy to lose them if your story gets a little slow.
I read it to my 8-year-old when he was 7 - he thought it was boring! That meant a big rewrite!
They're a difficult audience to please, and don't be under any illusion that they're easier to write for than adults - they're not, they're very discerning.