Port Royal, Darby Drydock.
Go to the Shipwright and walk in the wooden structure but behind the shack/counter.
You can then climb up the bow to the very top of the ship. Turn around to face the island.
You should see the "Wheel" of the ship on top of the shipwrights cabin.. fireworks will be seen immediately above that (approximately).
Best view of the fireworks i've ever had in POTCO.
I made a video of them from that spot here:
http://www.piratesonlineforums.com/f...ad.php?t=12220