I've run a 5-person several-hundred-$$ GB. Going to get a lot bigger next time around.
Major thing I can suggest, is keep your ducks in a row. When you update a spreadsheet, if you're actually using a .txt file on your PC -- update it too, at that same moment.
Keep any relevant PMs they'll help you sort out last-minute order changes. Reply to folks who're being unclear until you both know what you think the other is doing; don't spend your money on guessing what the other GH'er wants unless you can be okay about them backing out / clarifying it into something completely different.
Paypal allows $500 / month withdrawl without saying anything ... I haven't tried to lift that limit but somebody said it's not an issue until you get to GH60 sized $20,000+ being shuffled that you have to jump through way too many hoops.
(that would be a lot of PCBs. You could probably stage it into different months, y'know?)
Any other questions of a small one-time GB-organizer, you can ask me ... but there's plenty here who've run much bigger GBs whose input would still apply.
And, here's a thought -- you're open sourcing the switch file, right? So, after your first round or two, you could consider posting the file itself, or maybe OSHpark would 'publicize' the design for you. Smaller runs would reduce the cost savings but they could be ordered on demand by the user. It would depend on how quickly the per-board savings stacked up, and could overtake the shipping complications.
For myself -- I'm not sure I can get in (timing of my own personal finances) but I would want, if I got in, to buy ~200 boards -- enough for a TKL, a 60%, and some left over for a atreaus / ergodox spin-off thing. I'm sure others here think the same, so don't plan on "a few hundred" -- find the ~5,000 price tier and another around 2,000, maybe something sub-1,000 -- I bet if you tell us your personal MOQ is 6,200 switch-boards because reasons ... we'd hit it in less than a month of ordering.