SL-Mark: inviting them is not so much effort. Since there is a prize I expect a lot of interest, and players approaching me. All of you can point players out to me. I can then invite them, and all beginner's I come accross. I'm prepared to do the extra work involved.
I don't think you can exclude participants already signed up.
(hide) If you don't want other users to know what you are doing you can change into cloak mode in Settings (paying members only). (pauloaguia) (show all tips)