Sounds like an educational story for school child, with a transitioning class mate n therapy for the transitioning child.
But I probably wouldn't recommend you coming out like that, I came out by talking to the people most close to me, first my mum, she took it well, then my friends, they didn't take it well, it's just a risk I had to take for my own good, so coming out through a children's book is likely to add more risk to a negative reception to your coming out.
But what ever way you decide to come out, I wish you good luck.