If anyone was intending to write a children’s book I would suggest that they find out as much as they can about the type of book they are intending to write before they start. Check the book shops to see what is being published and by whom. I think it helps to have a clear idea of format and length.
It is possible to write about the same idea in different ways so if you want to be published it helps to know what publishers are looking for. After that, you have to write and rewrite until you are satisfied and don’t be put off by publishers who reject your work. Just send the manuscript off to another publisher and continue work on your next book.