From what I had on board when I sailed across, here is what I'd add to your list:

• The book(s) I never got to read (Proust, A la recherche du temps perdu).
  
• A star atlas and navigation tables so as to learn sextant navigation. We had competitions to produce the most accurate positionning, and we learnt the stars in the process.
  
• A waterproof camera, still and movie capable.

Pencil and paper were heavily used.

We decided not to give news to anyone, since when the system doesn't work, everyone worries.

Keeping batteries charged for electronics is a real pain unless you have wind/solar chargers. We had very little electronics; a wind vane steered the whole way.

Hot meals (pre-cooked at home) were much appreciated.

High quality waterproof 7x50 binoculars are a must. But you know that.