Well, it's customary to have the event include all characters since that is usually the point of all the events and a main theme of the game: to get everyone involved in something together. But as it has been in the past, there isn't any way that I can just make people participate in an event, nor would I want to force anyone to do anything that they did not want to do. SO yes, everyone will receive a cracker so as not to exclude any characters but no, they don't have to open them if they do not wish.