Read first, or watch first?
Read first, and this time we mean it, because the film rewrites the ending. A child who watches first will start the book expecting the father to walk back in, and the book's truer, sadder, still wonderful ending will feel like a mistake instead of the point. If the movie already happened at your house, one plain sentence before chapter one fixes it: the book ends differently, and see what you think of which ending is braver. Keep tissues within reach either way.