You can count on some people showing up at the door without a badge. If you turn them away they might make a scene and you don't want that. Sell blank badges at the door and let those folks write in their name.
Good luck at keeping this show a ODT secret. But I agree that it should not be...
It's desirable to sell all of the tables. You might try limiting each member to one table for the first batch of 50 then you can judge how much serious interest there is. If at some point you see that all tables won't be sold at "one per" then raise it to "two per" but give existing table...