When writing for children, it's important to consider all the ways in which a book will be used. Most often, picture books are shared through a group reading experience, such as when a teacher reads to a classroom, a storytime in a library, a bookstore event, or a parent reading aloud to children at home.
A good writer will consider the emerging reading ability of a child as well as the aural ability and context a child might assign to what they hear when a book is read out loud to them.
Years ago, I wrote a draft which included the line "The girl let out a wail." Now, for experienced readers who can handle this text independently, they will understand there are whales and wails. In this regard, the line might suffice. But this line is not the best choice for a read aloud. Why? When a young listener hears "The girl let out a wail" they may stop going forward in their listening posture because the aural message halts the contextual processing. The girl let out a wail? The young listener may initially think of the definition and context with which they are most familiar (whale), and stall to ponder the girl and the many ways and reasons for which she could be letting out a whale. Had she swallowed it? Is it locked in the closet? How did this whale get in the story anyhow?
From this, it's easy to see why the read aloud is critical to the success of a picture book. So what can you do to make sure there are no breaching whales in your story?
As you write and move through your stages of self-editing, read your story aloud. But don't just sit at your desk and read the text out loud in a hurried fashion. Simulate the classroom or library experience. Get a chair. Face the room and imagine you are a teacher reading to students. Set the timer. Read slowly and in the way you would read to young children - with expression. As you do this, those places in your manuscript that are heavy, clumsy, or include words or passages that may confuse a young listener aurally, will become apparent.
In short, a picture book must be as strong and concise for those who are listening to it as it is for those who are reading it. This is where children's literature becomes exciting and demanding at the same time. Many picture books appear in sight and sound as if they were easy to create - but anyone who's attempted to write for children knows that it is one of the most difficult forms of writing. The simpler it seems, the harder it was to create. And one of the best ways to keep your story simple as you edit is to read it out loud and assess how it works for readers - and listeners alike.