One per room or one per guest?
You can deduct this from your New Year's price ;-)!

Regarding the reservation question, I would not recommend to make any before being there. Look around and decide yourself. Only "The Rock" is very small (but do you like to sit together with other guests for such price?; just look inside before going there), the other ones were more or less empty during our stay (of course they told us to make reservations... that they can better plan!). Therefore, they close some restaurants during different weekdays to get the guests "concentrated" and "focus" to 2-3 restaurants.