I would make a note of this on your reservations and ask to speak with a chef when you arrive. A chef should come out and walk you through the buffet line explaining which items have higher or lower sodium contents. Chefs will not be able to give you exact sodium contents but they do know how much salt they add to each dish to give you a general idea. He may also be able to prepare lower sodium version of some foods that are on the buffet. Note that this is time consuming and slow but for somebody for whom dietary mis-steps can be dangerous, it's very much worth the wait.