Bro. Sweet -- By announce, do you mean something to the effect of saying "Hey, I'm going to the _________ cruise-in this Saturday! Who's in?"
I think that's about as good as it will get -- seems like last Summer, the few things we tried to plan as a group were impacted by everyone's fluid schedules.
We have a Wednesday cruisein here in So. MD that Peg and I only went to once last year ... (and that one seems to be for Corvettes and cookie cutter muscle cars/self-propelled boom boxes. Trucks are tolerated...)