To be honest, my thoughts on that are that you have to create an environment where no one CARES if people think they are gay by going to a meeting.
\In other words, if people there feel a need to say, "BUt I'm stright, not gay!" that creates an environment in which no one is allied at all.
Some of that also lies in creating dualism. The whole world really isn't satright or gay. I know that neither of those terms describe me, at all, to make it personal. The whole world is a million shades of greay in between -- bisexual, pansexual, homosexual with heterosexual experience, heterosexual with homosexual fantasies, omnisexual, asexual...I could go on for pages.
But what I'm saying is, in order to create an environment of openness, you have to really BE open. Sexuality isn't about having two sides of a single coin. So perhaps creating materials or an environment in which you simply work with inclusiveity EVERYONE can subscribe to, rather than making people "pick sides," you can get a lot farther.
So, if you;re making flyers for this or some such, why not have them say something like "Support Human Rights -- Support ALL Sexual Identnties," or some such.
And Hanne and I are always happy, by the way, to allow people doing things like this to print out some articles from here (try the gaydar section) for such use, as long as you let us know you're doing that and make sure our URLand copyright info is on the copies.