This cruise way a good way to see all of the Hawaiian Islands, at each port the malls have free shuttles taking you from the port to their part of the mall which is handy.
If you plan to go to the beach on any of the Islands I recommend choosing the beach you want to go to beforehand and figuring out how you will get there form the port before the day you go.
We didn't do any shore excursions through the cruise line so cannot comment on those but we booked the Circle of Fire tour over the volcano on the Big Island with Blue Hawaiian Helicopters, we spent a bit more and went in the Eco Star and I think it is well worth it.
We recommend this cabin as it is well placed on the side of the ship you want to be on. Plenty of room for 2 of us, bathroom is decent size keeping in ind you are not in a suite on a ship just in a cabin - but a decent cabin, if you are not sure about a balcony you will regret not having one.