So jealous! We did this on the Crystal Harmony (20 days) in 2000 from SF to Sydney.
In Apia (Western Samoa) be sure to take the trip to see Robert Louis Stevenson's home. We also went snorkeling at the small park right near the pier (walking distance) which has bathrooms and changing areas, rents equipment, and has a classic South Pacific beach and reef, as well as picnic tables in the shade. We had a great time. Other than Hawaii and Samoa, we had different ports than on your trip.
We love days at sea. In our 15 sea days we saw only one other ship the entire trip. We were fortunate and it was smooth and clear nearly the entire trip