There's musical fat quarters - you have to pass them on (or toss them across the room) until the music stops. whoever has it when the music stops can keep it.
Bingo - make a chart like a bingo card and put a task in each square - like "use seam ripper", "broke a needle" " poked my finger with a pin" "finished a block" "finished a row" "applied binding" "changed the bobbin" "ran out of bobbin thread and didn't notice," etc, etc..
As someone finishes one of the tasks she gets to shout it out loud (the louder the better) and cross it off her chart. Whoever has the chart full first, or has it filled in the most, at the end of the retreat, wins a prize.