I second this!! It is your vacation and if you want to be a little more dressed up so you can enjoy the experience more and be happy with your photos... Go for it!! A cardigan is a great and simple option and one that I think you'll be happy with.Personally, I think the key is to wear what you'll be comfortable in! If you'll feel more comfortable getting a bit dressed up for dinner, go for it. You'll see the whole gamut on an ABD. I'd just recommend getting a cute cardigan to wear over it, as otherwise you may get really chilled at night.
Sayhello
I always dress up when I can on vacation because I work in a lab which means jeans and a lab coat are my attire. When I go on vacation I enjoy dressing up a bit so I can look back at photos and be happy with them.
Do what will make you happy and you'll have a fantastic trip!!! Enjoy yourself and please do post on your experience. It sounds like a fantastic adventure.