54 pieces of 2 by 4, each cut to a length of 10.5 inches. Make sure they are pretty smooth, you may sand them down to smooth them out a bit. You could also put some baby powder on each board to make it slide better.
Set them up like the Jenga game and have all the kids have a go at the game. I added a hammer to the game and gave each kid only one chance to use the hammer to help move a board if they needed to.