This is a "join in anytime" game the boys can play as they arrive. Here's how it's played.
The boys sit around in a circle. One person is given a calculator to start. He punches in a number (any odd number from 1 through 7) and presses the + key. He passes it on to the next player, who does the same thing. This continues until the value reaches 50. If a player presses a number that causes the total to exceed 50, he has to pass it on to the next person to start. If he selects a number that gets the total to exactly 50, he gets to start the next round.