It would certainly annoy me if I were eating dinner in a restaurant, and a group of people came in with flags and "chants". That is not appropriate behavior in the common dining room of a restaurant.
They should have either rented out the restaurant for the evening, or found a venue with a private dining room (which Olive Garden restaurants don't have AFAIK) to hold their ceremony.
Chants!
Where did that come from. I didn't read anything about chants.