We do this a lot, but haven't done it at Sci-Fi yet. We make sure to go at off-peak hours, though the new Dining plan seems to be crowding out a lot of the table services restaurants, I'm not sure there is an "off-peak" anymore, so we may hesitate to do this for our next trip. I would just wing it and stop by to ask the CM. It's also always helpful to give them a timeframe. I usually say that we won't be longer than 15-20 minutes for coffee and dessert.