Don’t upgrade. The Haven 2-bedroom is fine for a family of two adults and two kids, but in my opinion is unsuitable for six, particularly if more than two adults. Would you put your mother on the couch bed with another person?
I suggest the Star out of New York to Halifax, St. John’s, St. Pierre-Miquelon (French islands), Greenland (3 stops) and Iceland (3 stops). Follow up with a few days in London.
In 10 cruises I have found reserving a table in the MDR to be a complete waste of time. Usually seated immediately and never had to wait more than 15 minutes—with or without a reservation.