Hi there. We have sailed twice on QM2, both occasions in a P2 cabin, numbers 10127 and 10123. the cabins are quite spacious with lots of storage space for clothes, suitcases etc. They are more square in design which means that you are not having to squeeze past the end of the bed. The layout shown on cunard website is fairly accurate. I am sure you will not be disappointed with the facilities. The bathroom is a good size with under basin storage for toiletries etc. The only down side is that the shower is over the bath which itself is quite narrow. However it is not a huge problem and you will easily adapt.
Princess and Queens grills are separate. They are both on deck 7 but on different sides of the ship and they share the galley in between. The menus are very similar with perhaps an extra choice of entree in queens grill. However as well as the set menus in princess you are able to choose from an a la carte menu so there is plenty of choice and the food is superb. I believe that in Queens Grill you can ask for items not on the menu and if you have a problem with what is on offer they are very flexible in princess grill as well. Be sure to try the flambe dishes, i can certainly recommend them. Single seating means that you can choose whatever time you like to go into the restaurant. you will have the same table every night but if your dining companions have not arrived or already started their meal it will have no bearing on you. We had a table for 2 the first time we sailed and just recently we shared a table for 4 with our travelling companions. If you have strong feelings about wanting a table to yourselves please speak to the maitre d' as soon as you embark. he is usually able to arrange matters to your satisfaction.
When we arrived back in New York from the caribbean we were staying at the mandarin oriental, which was fantastic. We arrived at the hotel at about 10 am and our room was available immediately. Even if the room isn't ready you can leave your luggage with the bellhop and use the lounge/bar etc or do some sight seeing and then return to the hotel. I am sure that you will be able to do this at the hotel you have chosen to stay.
I am not sure I would recommend waiting until the last passengers are due to disembark unless you are arranging your transfer to the hotel yourselves. If cunard have arranged the transfer for you they tend to group people in the same hotel together so they disembark at the same time. That way you will not keep others waiting in the coach or risk it leaving without you. If you did want to transfer yourselves you could wait till the last passengers and a taxi would cost you about 50 dollars.
If you have any other questions please feel free to contact me by ###############. I would be happy to help and can also send you copies of the princess grill menus if you would like.
In closing I would say that the service and food were outstanding, the cabin extremely comfortable and of a good size and the whole experience fantastic. I have written a review which you can read if you want to know more about the trip.
Sorry for the delay in saying thanks for the above info as we are arranging our own transfers we may pre-book our SUV to meet us for disembarking as we have another 3 days in NY after the cruis.