I'll offer a cautionary tale that this doesn't always work. While staying at BCV this past summer, I asked about adding my parents to our room. Adding them would have made 4 in a studio, so we were within the official occupancy. We weren't on any dining plan. The front desk wouldn't allow me to do it. I also called MS, and they also said it couldn't be done.
Fortunately, it didn't cause us any hardship. My parents had a room at their own timeshare. I was just trying to add them to our room so we could do SAB together.