They are also taking part in "Pirates Ashore" on May 21st with several other local organizations. This commemorates the coming ashore of some 80 English privateers (technically not pirates) in 1646 & the ensuing mayhem. Cannon fire and suchlike will be at the pier and the pirate encampment (presumably where the grog will be) is to be on the grounds of the Mayflower House (GSMD HQ.) Singing entertainment will be at the nearby Spooner House, run by the Plymouth Antiquarian Society, and various misbehaving pirates will be roaming old town Plymouth. This is free and open to all, and runs from 9:30 to after 3:00 pm. The "rain date" is May 22nd. For more details, see the Pirates Ashore page on Facebook.
If this is as much fun as it sounds and you live somewhere in the area and can get to meetings and events, consider becoming a member. "Able to fire a cannon" will look good on your resume.