The first large-scale organized meeting, occurred on Monday, November 29, 1773 at Faneuil Hall. Thousands of men, women, and children gathered from Boston to meet at Faneuil Hall. The Suns Of Liberty organized the meeting. So many people attended the meeting had to be moved to the Old South Meeting House.
During the meeting they discussed how they would dump the tea, They also discussed costumes. They also made it clear that they would not destroy the ship. They were just destroying the tea.
They changed into costumes to not be recognized. If they were recognized as colonist, they would not of been let on the ship.