Hello, I'm Alberto Palacios, guitar player, composer, singer.
I can definitely transcribe your original song into a keyboard score or even tablature with Guitar Pro (in a single day I'm guessing), and compose an easy going children song based on some aspects of your book (I use tablatures, but they get transcribed instantly into scores).
I'm guessing your song is in a Major scales right??, should be done real quick, we can check and re-check the lyrics but it'll be done ASAP (my bid is on 7 days but I think it could be probably 3 or 4).
I'd be sending you a PDF file with the score transcription or maybe, if you want something more "commercial", we always can use this format (or both):
"Children song" A - D - E - A
A D
Here goes the music of the song
E A
A children song just for you
A D
Based on a book I just wrote.
E A
Because I care, and so do you.