A clear vinyl map pocket that clips to your handlebars is a nice thing to have, or a vest pocket where your route info can be in easy reach, in case you are separated from your group.

Pack light. If you overpack, you're going to have to lug all that extra stuff around. If you forget something, you can probably buy what you need.

I'm so jealous and hope you have a great time! Eat lots of yummy food and post pictures when you come back!