Hey, here's another thought maybe....
Might ask around a little at Cabellas and find out if you could put up a flyer near the front doors a couple days in advance. I know a lot of guys who shoot trad don't have computers but I don't know many of them who don't pop into Cabellas every once in a while. Might snag a few more that way. Might also get a couple to show up who don't shoot trad yet but have been thinking about or are just curious. It's been my experience that if a guy is even a little bit interested in trad all you have to do is get them in contact with somebody who actually does it and let the hook set itself...
Cabellas might be very favorable to this simply because if a fella got bit by the trad bug, "Well gosh, there just happens to be a nice modest selections of trad bows right downstairs. Come on and I'll show them to ya."
And for THAT purpose, the shooting lane is more than sufficient.
p.s. I think I still have the lists somewhere that we made up in the past when I had the other get togethers at Platte Falls. Should be about 15 names in all with phone numbers if I can find them.