For my sons 5th birthday we had a pirate party.  I made the invitations on beige colored construction paper, copied a message out of a party book -"the young swashbuckler----is requesting your presence at a PIRATE PARTY-secrete location, date and time. Burnt the edges to look like an old map, made a separate map to the location, rolled them together, tied with string. We had a treasure chest cake(layered square cake) with chocolate coins and beaded necklaces overflowing the top.  We had a treasure hunt. The clues were in envelopes, one was a written clue (for me to read) the other a picture (cut into a puzzle)the answer to the clue. When they found the treasure chest, the children were lined up, given paper lunch bags, and the chest was dumped out like a piñata.