I haven't been to this particular Pontiac event (yet), but I have been to Branson several times and have been to large car events there. It would be a good central place. I think piggybacking a larger event might be good too. Maybe this time next year.
From a more fair view, once a good amount of definite attendees were compiled, the "central" location should be derived based on the distance from the largest group of attendees.
For me, if it were more than 5hrs from Fort Smith Arkansas I would not be able to attend. Just don't have the time or cash to make such an outing.