The Big Island of Hawaii, Hilo and Kona. Read up on Kilauea Volcano,the volcano national park and Puna beaches before your departureon, on the internet. Go on a tour its worth while.
I agree with the answer given - BUT its a big BUT. I did this trip in September on the Diamond and quite simply the Diamond Princess is too big for this route and many passengers were disappointed not to get on the tours. There are not enough buses to transport everyone around especially if there is another cruise ship in port on the day, particularly in Hilo. As soon as you can, book the tours you want on line. It is totally no good leaving it until you get on board or you will be disappointed. There is so little transport you won't be able to hire a car either unless you do so well in advance.