Don't need to reinvent the wheel, the way its been done in other swaps is the central person collects all the seeds. Participants indicate if they want extra bonus seeds. Everyone who sends in gets their requests. If they don't send in they don't get seeds. Those who indicate they will accept bonus seeds gets the extras.
As for timing, we all have seeds collected now. We can do the swapping in November then have seeds sent out in January, it takes a while to get them all mailed in and divided. In time for zone 7 and above, which is not just the south but includes Long Island NY. National Seed Swap day is the last Saturday in January, which is when I'm doing a local swap. If swap is done so late in season will lose a lot of us zone 7 plus. In the end whoever is doing labor will do how they see fit, but I'm sharing my experience of what worked in other swaps.
