With a large rope (or use a square in the dirt or whatever you can find) make a large oval or rectangle.
Assign each side what it is called (port, starboard, aft, bow). The inside of the circle is the poop deck. Call out a side or poop deck and the kids have to get there as fast as they can. The last one there has to sit out (or some other physical activity). If you give the order of ÛÏcaptain on deckÛ the entire group has to stand at attention while saluting. If they move at all before you say ÛÏat easeÛ then again they sit out.