Sounds like a nice trip.
I appreciate that it's a no-brainer, but I will mention the hot drinks and handy high energy snacks. A 6m rib in midchannel is no place to get hungry or cold. I'm sure you have a First Aid kit. I tend to carry a simple passage plan and a handheld GPS, just in case a power issue takes the instruments out.
When "alone" like that, I carry a few things on my person, secured with lanyards, in case I go for a swim...
1. Handheld VHF
You'll have a ball