If the theme that you want to argue for is guilt leads to good, then I can see how it works in the Kite Runner, but it is harder to see in the Atonement.
In the Kite Runner, Amir goes back to Afganhistan and faces his demons. He confronts Assef and even risks his life doing so. When he finds out that Hassan was killed and he finds out that he had a son (Sohrab), he takes it upon himself to find him. Amir knows that Sohrab would undoubtedly live a horrible life under Assef and the rest of the Taliban. Amir brings him back to the United States and adopts him.
In the Atonement, Briony falsely accuses Robbie Turner of rape and thereby causes a divide between the love between him and her sister Cecilia. Robbie goes to jail and eventually gets out only to spend a few moments with Cecilia, who is not in speaking terms with her family. However, due to the war, both die. Briony knows what she has done and refuses her place at Cambridge and becomes a nurse. She also writes a novel and in this novel she bring them together. I suppose that Briony does good, but her good is not something that is directly related to Robbie and Cecilia. In light of this, the Kite Runner possesses a strong view of good.