Since the menu changes, if we et there and there isn't anything I would eat, can you just get dessert?

I was wondering about dessert there, too, and if you can get PS seating for dessert only (or do you just not mention it?)

You can order just dessert in any table service restaurant at the hotels, you are not required to purchase a meal except during character meals. You can also make a PS for anything you want, you do not have to order dinner just because you have a PS.