I get a lot of questions about a child’s music development. The best book I have found is “Your Musical Child: Inspiring Kids to Play and Sing for Keeps” by Jessica Baron Turner.
You can start anywhere in the book and it’s written with the right amount of theory and practical information for parents with children of all ages. It answers the following questions: “What makes a child fall in love with learning to play music? How does talent develop? When is the right time to start lessons? Which instrument is the best fit? Why is practice so challenging, and what can parents do to keep kids musically motivated? Where can a parent learn about music programs, camps, books, recordings, and other important resources?”