Break team into games of 3 players verses 3 players or 2 verses 2 if you have lower numbers. Fields should be around 20 x 15 yards with a goal on each end. Adjust for numbers.
Each player gets a number (example 1-24). Split into teams of 3 at random. Kids get 3 points for a win, 1 point for a tie, and 1 poiont per goal scored in the game. Coach asks at the end of each game how many points they earned, record it on paper. Split players up into random teams again and repeat point system. Player with the most points at the end is the winner.