Writing for kids is different than writing for adults.
Sure, much of it is the same - those "rules" of writing, like show, don't tell, resist the urge to explain, etc.
But writing for children has its own unique challenges.
I've often compared writing for children to writing scripts.
But it's also much like writing short stories.
I recently found a quote that puts into that into words perfectly:
From Off the Page, quoted by author Walter Mosley:
And so, when writing a short story [or children's book], you have to know everything behind it - everything that led up to there, everything about those characters. But you don't have the leisure to talk about it at length. You only see that very upper tip, as with an island compared to the mountain that lies underneath it.
It's imperative that you know the background of your story and your characters.
But you don't need to - in fact, you probably shouldn't - write about it.
It should be "invisibly present" - like a rippling undercurrent beneath the still waters.
How you accomplish that is a matter of personal taste. Some writers do exercises like interviewing their characters or making lists of the characters' favorite foods and hobbies and what's in their backpacks.
I just think a lot.
So by the time I sit down to write, I know my characters inside and out.
I know what happened the day before the story started.
But I don't write about it.