You are now on the Mêlée Island™ dock. As you try to reach the church, you will be confronted by at least one ghost pirate, but the magic seltzer will dispose of them. The second ghost pirate—the grim spectre—may be avoided by taking the blue door on the left.
Upon entering the church, interrupt the wedding. After exchanging a few words with LeChuck, you will be tossed around the island before landing near the vending machine at Stan's. After getting back up, do not walk, or else LeChuck will quickly knock you into the air again. Instead, quickly pick up the root beer (a green bottle) on the floor, and use it on LeChuck. (If you fail to do so quickly enough or walk, LeChuck will keep beating you around the island until you use the root beer on him.)
LeChuck is now defeated, and you get to enjoy your final talk of the game with the governor while the fireworks explode.