Sounds like a fantastic trip. "A Three Hour Tour, A Three Hour Tour ...." you say ? Better pack some coconuts just incase !
And:
I know you mentioned intermittent phone coverage, so it would be worth getting some local numbers.
If you do have an issue, a local call to a marine mechanic, local police, boat club, onshore friends etc may be more appropriate than emergency services.
When I'm on the water I try and take a knife with a (half) serrated blade - better for cutting ropes and webbing
Do you need anything for sea sickness ? Crystalized ginger and peppermints are good "remedies", and good to add to your snack pack. They both assist with motion sickness, but if you travel with a "real" sufferer, then you can't beat real meds (IMO).
As to packing all that gear, what about a survival vest format ? It means you will always have it on you when the boat sinks !