I think it's a great idea, but given the wide area that the members of a group such as this will come from, I doubt that it would get the attendance.
One problem with organising these things is that people will say they'll come, and then not turn up. I've seen events that groups have organised where twenty people said they'd go, and the organisers have ended up with just one person.
It's a great pity, but it seems to be a fact of life.