There is an interesting sounding exhibit these days, through Jan. 27 at the Morgan Library & Museum, 225 Madison Avenue, at 36th Street; themorgan.org. of Beatrix Potter's letters to young friends. The premise is based on illustrated letters of that era, and includes some by others to demonstrate that there was a tradition of sketches along with the message. As well there is consideration given to some of the spinoffs of the Potter empire, including a board game. NYT story here
This brings to mind the fact that the tale of Little Black Sambo was written as letters to the children back in England from their mother while she lived in India. And I believe that the Peter Pan stories were in some part begun as tales to entertain young friends. Small efforts that spun off to take on a life of their own once out of their creators' collective hands.