We don't go to the dining room for departure breakfast because (1) it is too early for us, since we always choose the first seating time (2) the menu is limited (3) the meal, I hear, can seem rushed, and (4) we love the great buffet choices, relative quiet, view and leisure of Cabanas.
We, of course, always tell our servers we won't be there. Tips are handed out the night before so that isn't a concern.