Yesterday I instituted "round-robin". The kids were fighting about what they were going to play and who was going to play it. I had them pick a number between 1 and 300 to decide who goes first. Then they each got to choose what they wanted to play. By order of the number they picked they played with each other each person's choice for 30 minutes. I set a timer for each time period.
I got 2 hours of FREE time for me to exercise and work!
On slow days I think I am going to play with them, they sounded like they were having so much fun:)