Actually, attendees of events at OCCC don't usually get down to WDW during their conventions except for special parties; they are more likely to visit WDW in the days right before the meetings start or right after their conventions end. If they are doing parks in the evenings, Universal gets the bulk of the traffic, because it is closer, and more likely to have given the planners a good price for a private event. (And because lots of people fall for the idea that there is no point in going to WDW if your kids are not with you.)
While some attendees will bring families who will go to the parks while Mom or Dad do meetings, it's usually well less than half during the school year. Most people who are there for conventions actually do go to the sessions, and it takes too much time to get down from I-Drive and into the parks unless you can stay for several hours.