I already went through the effort of typing this up so I figure I'd post it. We might be passed the point of no return for something like this to be viable but people might enjoy the idea anyway.
Instead of doing the throw information everywhere for free thing with the posters I think we can be significantly more clever and effective.
Expanding and formalizing upon the earlier auction idea I had:
In the last hour or so we get Bonku to set up an "auction game for fun" to auction off " the location and guest list of the next party" to the highest bidder. Very suggestively hinted to be an info list of secret identities and the location for the next event.
This will be a sealed-bid auction (so you put your bid forth in a sealed envelope, and the highest bidder wins).
The bidders will be bidding information about current guests. They will be required to put down (Name, Job, Country, Funny Nickname, Their Childhood dream) for as many number of people as they want. The express purpose both implied and all but stated is that you will give some permutation of information that will identify someone in the actual event. This will be checked against a pre-compiled master list (which has some degree of correctness but is nonetheless rigged and that we have the answer key for)
In character the point is just a fun game to see who remembers the most about guests from the party. We can do this through Bonku reading the bids, so anonymity is preserved. He is running the show here, announcer and everything.
We can attend the auction so no one knows it is us behind this. In fact, we are encouraged to attend so that this appears both legit as well as an eminent danger to everyone not in attendance.
We will have Bonku check the information off from a list we provide (this doesn't need to have correct information, in fact its a fucking sham) to determine the highest bidder. The winner (it must be Hazou, rig it) will get the "list" and the location of the "next party" (we bullshit that in character).
Bonku hands the "list" off to the winner (Hazou) who palms the bids and leaves.
Why the fuck would anyone do this?
1) If they see anyone else playing along, they are at major risk if this is real.
1a) If they have the brains to think game-theoretically at all they will be all but forced to go along with this.
1b) It will still stress them the fuck out.
2) They are not compelled to bid anything but its to their advantage to submit a decent chunk of info. They might win.
Why the fuck would we do this you might ask?
1)Simple, we get the bids afterwards, so we can both double check our info as well as statistically verifying info that we don't know. If 8 people put the same points of information for someone for example, then we most likely have them dead to rights.
2) This prevents anyone we haven't already duct-taped drunk goggles to from deciding to go the nuclear option at the last minute, hopefully.
2a) Anyone we have drunk -goggled might just decide this is for real and spill all the fucking beans anyway, jackpot.
3) We can just rig it so that whatever info Hazou gives is identical to that of the list's anyway.
4) This should gather people together for a last ditch plot if we need them centralized once again.
5) We just have to have a decent portion of our group show up for the actual auction and forge the info list. Bonku can handle the rest. Its almost zero effort from our part.