How do the children react to Atticus’s hidden identity? How does their perspective change? Why does Atticus refuse to use his talent? What does that say about his morality? How does it make up part of his identity

I assume you are referring to Atticus' talents as a marksman? When Atticus is forced to take action against Tim Johnson (the dog), he reluctantly takes aim before shooting him. The dog crumples into a heap, and Jem is dumbstruck by the accuracy of his father's shot. Miss Maudie tells the children that their father used to be known as "One-Shot Finch," the best dead-shot in the county. She says he doesn't shoot unless he has to, because he feels that when he holds a gun, God has given him an unfair advantage over living beings. Scout wants to tell everyone in school about the incident, but Jem tells her not to. Jem explains that he wouldn't care if Atticus "couldn't do a blessed thing," because Atticus is a gentleman.