What celebration do Amir and his family attend? What does Amir buy at his celebration? What happens at this celebration that makes sohrab smile?

Amir and Soraya took Sohrab to an Afghan picnic in the park, along with Khanum Taheri. General Taheri was not there because he had finally gotten his wish; he had been offered a post in the Afghanistan ministry. By now, people had gotten used to Sohrab's silence and even Soraya could not bear trying to engage him anymore. Only Amir kept trying. Suddenly, Amir noticed kites flying over the park. He bought one and brought it to Sohrab. He told him that Hassan was the best kite runner he had ever known and asked Sohrab to fly the kite with him. Sohrab remained silent, but Amir knew what to do; he ran as fast as he could to launch the kite. As he stared up at it, he noticed that Sohrab had followed him and handed him the string. Sohrab soon gave it back to him. They stood in silence once more until they noticed a green kite closing in on theirs. When the kite came close enough, Amir performed Hassan's favorite kite-fighting trick, "the old lift-and-dive" as Sohrab watched, mesmerized. The green kite fell out of the air. When Amir looked down at Sohrab, he witnessed a half-smile steal over Sohrab's face. He asked, "Do you want me to run that kite for you?" Sohrab nodded, and Amir told him, "For you, a thousand times over." Amir ran among the children, after the kite.