I've never used the Vistana shuttles, but I have asked about it. It's approximately $8/person/day. They do have "set" times when they go into the parks and then pick up later in the day. I had the times from 2007, but not sure they are still the same schedules. I would inquire at the lobby concierge desk for specific info on this. But I recall they left at approx 4 different times in the morning and then again picked up about 4 different times in the evening.
Maria