I would email the ones you have, call the numbers you have and then send out postcards to the rest, even if they are old addresses they may be forwarded, or the parents may even let you know the new address which occured several times when I started Omaha's JC.
You could even try (if you have the time and patience) making a flyer on your computer and hand deliver them into the mailboxes of those close enough to you. I would prefer the postcards though because then you know who to cross off your list!
I hope you have a very successful organizational meeting!!!

Let us know how it goes!!