Thank you so much for the quick reply. We chose late dining when we booked, and there is a recent discussion about dining which says your allocated table is on your cruise card, and I am sure I saw mention of having a reserved table in the MDR on the MSC website.
It's a 4 night cruise, and we'd probably want to do a speciality restaurant on one night, which we can only book when get on board, and we'd want to try the buffet one evening, so may only be in the MDR on 2 nights. I was assuming we'd decide on the day which night to try the buffet, depending on how the day went and what we want to do in the evening, but if we are expected to tell the table or maitre d' the day before, maybe we need to decide before the cruise. Unless it's possible to pop to our dining room in the evening, before our dining time and tell them we won't be there?