I had asked my Dad to build a simple cardboard boat for me. He went a little overboard and made a cardboard/duct tape boat that was capable of floating in the pool (even if floating in in scared the crap out of most of the kids in attendance). I taped on the sail from a big square of fabric.
Pirates love marshmallows.
I did chocolate cupcakes with mint flavoring added to the frosting.
I made the sails from paint sample cards and craft sticks.
Newspaper hats served as a party favor as well as decoration.
I just paper clipped them onto the twine.
I put up some dotted fabric and we took individual photos of the kids
with the newspaper hats on.
I luckily only had time to make two newspaper swords. Which was
probably just enough with the young and wild crowd of cousins we
had in attendance.
The kids swam, ate pizza, chased each other around, and finished up right before the rain started. I think it was pretty simple and pretty perfect (not to mention CHEAP).