You misunderstand the dining. It isn't 2 options every night. Normally the 1st night is in the dining room and from then it depends on the weather. For the 10 course degustation menu it is also in the dining room. Shorts are allowed for the outside dining, though usually something nice, not t-shirt and cargo shorts. Dockers and polo are OK, more will be wearing short or long-sleeved shirts. The dining room is also quite cold.