Here are some good free teaching resources for International Talk like a Pirate Day:
Check out the play "The Pint Sized Pirate" about a small pirate with big dreams. It teaches how someone who is little can still make a difference. Check it out for free at this link: http://www.freedrama.net/pegpirate.html
There are also theatre games (aka improv) that is a lot of fun for kids and gets them up, moving around. It's fun way to introduce drama to kids. Here is a link to some fun free pirate improv games: http://freedramaplays.blogspot.com/2013/12/pirate-improv-games-fun-drama-classroom.html
A pirate theme unit is a great way to teach map skills to kids. Have kids hide treasures and make maps that other kids have to follow. Or teach some geography. When I was teaching elementary school, I often made my own board games using maps... kids roll the dice and see who can make it around the world or to all 50 states first.
Your unit can work with almost any topic. Read stories about pirates, write your own pirate stories, learn about historical pirates, learn the science of sailing and cannons, and use math to count treasure and measure distances for maps.
A good time for this theme unit might be September since September 19th is "Talk like a Pirate" day. If Krispy Kreme is still giving away free donuts that day, plan a field trip to one of their stores.