How about the weekend of August 26, 27, 28th...that's a couple of weeks away and would give everyone time to figure out what they've got, how much they want for it, etc.
There really is no planning here, other than to make everyone aware so they can list items or shop the Classifieds on those dates for some good deals.
The best way for this to happen would be the for Administrator or Webmaster to send out an email to all forum Members (that's how it was done on the previous forum I spoke of)...anyone got an "in" with the Admin to see if he can make this happen?