There is no real way to make the celebration end, so the player just needs to allow a certain amount of time to pass. They can do this by talking to the villagers or simply doing nothing (though each villager does have something unique to say). After some time, the Mayor will give the player a Firefly Light, which the player and villagers release into the sea.
If the player is trying to woo a certain bachelorette, the one they have the highest affection rate with will ask the player to walk them home. If the player is married, they will instead escort their wife back home.