Which three boys decide to go up to the mountain and what do the other boys do Lord of the Flies?

One of the first things that they decide on it that Ralph should be their chief. Ralph then appoints Jack to be in charge of the former choir and asks him to decide what they should be. Jack decides that they should be hunters. Finally Ralph says that they need to decide if they are on an island or not. He then chooses to take Jack and Simon with him on an expedition to find out.