Nawiliwili, Kauai is really the name of the harbor rather than the name of a town. The port lies outside of Lihue, the main town on Kauai. While the port resides in Nawiliwili Bay, so does Kalapaki Beach, which is the home of the Kauai Marriott Resort and Beach Club and an excellent beach as well.
While Nawiliwili resides more towards the southern end of the island, it still experiences a fair amount of rainfall receiving almost 50 inches in an average year. The mountain at the very center of Kauai, Mt. Waialeale receives so much rain each year that totally unique flora and fauna exist in the Alakai Swamp at its summit. Receiving over 600 inches of rain per year (that's right 600 inches) Mt. Waialeale is considered the wettest place on Earth.
Kauai has many things to enjoy. The ship will offer many excursions and you can also find a local tour operator in the shopping plaza on Kalapaki Beach. I believe the best tour for everyone to take would be the helicopter flightseeing tour of Mt. Waialeale, the Alakai Swamp, Waimea Canyon and the Na Pali Coast. The ship will certainly offer this option but there are several opportunities to choose from. In my opinion the optimum place to fly from is the small Hanalei/Princeville airport, as you experience fabulous scenery from the moment you take off. It follows a foot trail up Hanalei Valley into the mountains finally arriving at the Alakai Swamp before dropping into the Waimea Canyon. It is simply a trip to remember.