I suppose the suitability of Grafton vs. Taghkanic for a day event could depend largely on how close the potential attendees are to each lake. Maybe some sort of preliminary roll call, or a poll thread, would be in order to get a handle on potential attendance. Taghkanic is much closer for me in northwest Connecticut, but I'm about a medium probability attendee.
As to date, I think September after Labor Day would have a much reduced population of both beach goers and campground users everywhere.
As to date, I think September after Labor Day would have a much reduced population of both beach goers and campground users everywhere.