I am neither a DG nor an alum, but maybe local civic groups could be involved instead of fraternities. You could have the Masons, Shriners, Elks, Kiwanis, Rotary, Lions, and on and on. Many businesses or workpalces might form a team as well. I know when we did Big Brothers Big Sisters bowl-a-thons the intra competition was fierce but freindly.
But please make sure no one smacks anyone else in the head with a catfish