Your son does it very well, I love children's drawings when they are little, they show so much creativity, they put on paper the way they see the world. You know that the way they make their drawings shows their personality, psychologically they say that if they draw small, they are shy but if they cover the whole page, they are not shy, and I think it is true. My big daughter made small drawings and she is sometimes shy, and my little daughter paints the whole sheet, her drawings are big and very colorful sometimes, and she is not shy at all, hahaha.