In case it helps anyone in the future, here's what I've found so far:
For multiple user video chat you must use a iChat on all systems, and must see the multiple video icon next to the username you want to include in a video conference. IF you only see one video icon, then you can only do a one on one conference. The image below shows both, the upper video icon has a several layers of green video icon, this indicates that I can partake in a mutiple user conference with video. THe lower icon in the image just has the single video icon, which means they can only do a one on one.
Also, screen sharing only works between iChats, not iChat and AIM.
