Your cards are adorable! If everyone makes their own card maybe they should be required to make a key for it so they remember what they intended each square to be. At our quilt retreats we play bingo. We each bring 20 2 1/2 inch by wof strips. For each game we turn in 2 strips. Then we play bingo with ordinary bingo cards. The winner of the game gets the pile of strips. It is fun and hard to cheat.