Hmm...I am not sure if you can through IM software connect with both iChat users and PC AIM users at once.
Have you heard of
MeBeam Video Chat? You create a name for the room, click connect, and the site automatically searches for your webcam/microphone. I have used it before and it is somewhat decent, and free. You can type text in MeBeam also.
Make sure you create a very unique room name, if you want the conference to be kept very private (e.g. Meeting393845423). Just tell users to meet you in room "Meeting393845423" On X day at Y time, and you'll be all set.
Oh, and using headphones and a high-speed internet connection will help.
