There's a certain key that will submit it for you. It happens to me a lot of times.

Make it a masquerade ball meeting theme. Everyone shows up wearing complex costumes and masks, both of which have subtle clues about the person's personality, and no one is allowed to say who they are while the meeting goes until the end.

Or, fort making theme, and everyone brings a bunch of chairs and blankets and makes forts. When it comes time to actually do the meeting, everyone must use tin can telephones. After the meeting, all the people will group into two teams and there will be a rolled sock throwing/Nerf gun battle that will end with watching silly cartoons while eating popcorn and drinking hot chocolate.

Or! Dapper gentlemen them: everyone shows up with ridiculous mustaches that they made, monocles, and top hats (full-on dress suits and pocket watches are also recommended). People then start the majority of their discussions with "I daresay!" and refer to each other as "old chap".

-Nukaya