Ask HN: A good “group management” tool?

Hi all, I'm not sure the best way to ask this question. I'm organizing a trip of about 15 people and the logistics are getting a little insane.

I'm wondering if there's a nice tool out there for managing a whole bunch of people and their info. I'm responsible for booking travel, keeping track of people's frequent flyer numbers, etc.

Bonus points if the tool has a chat/group messaging functions, particularly channels and DMs.

Thanks!