The Real Howard Spitz (1998) on Netflix

Plot summary

Howard Spitz writes detective novels that do not sell, and his money and luck are gone. Noticing how well children's books do, he decides that writing one will be simple, and invents a bovine detective called Crafty Cow, but the work proves much harder than he assumed. At the local library he hands his drafts to Samantha Kershaw, an eight-year-old who tidies them up. In exchange she wants his help tracking down the father she never met. Spitz also learns that children's authors must appear in public before their readers, and the thought of time among children frightens him.