Plastic swords are a cheap buy today and add some authenticity worn with a pirate costume. Have some ‘organized’ sword-fight. If a few children are left alone with plastic weapons without a little supervision then it is only a matter of time before one of them is wounded… Perhaps, to avoid any squabbles, you can have some proper contests for them where they are able to show off their swordsmanship to the fore.
If you have your children’s’ party in the summer then another idea would be to have some themed games in the back garden. With a bit of imagination, you can soon adapt some ordinary children’s activities into something that is more in keeping with pirate costumes. Perhaps you have a sandpit where you can bury some ‘treasure’. The kids will love to dig away hoping to be first to find it, especially if they don’t even know what it is that they are looking for.
With a little thought and planning (and minimal outlay) you can easily create a whole afternoon of fun that everyone will thoroughly enjoy