Kaua'i
Kaua'i is called the Garden Isle. There is a reason for that. If you have an image in your mind of what Hawai'i is suppose to look like, you are probably imagining Kaua'i. At 552 square miles, it only has a population of 67,091 full-time residents. Most of that population lives on or close to the coastline. There are 90 interesting miles of coast, of it with jagged cliffs and remote beaches.
The main tourist destinations are Princeville in the North, the Coconut Coast on the East and Poipu in the South. If you think of the Island as a clock face, Princeville is at 12 o'clock, Poipu at 6 o'clock and the Napali Coast is from 9 to 12 o'clock. No roads there. The center of the Island is Mt Waileale at 5243 feet. This is the wettest spot on Earth, with approximately 40 feet of rainfall each year. This explains why the volcano is the only one in the world with a swamp on top, the Ala'kai Swamp. The top of the mountain can be visited by the road up the ten mile long 3500 foot deep Waimea Canyon, which was named the Grand Canyon of the Pacific by Mark Twain on his visit. There are over 40 miles of hiking trails, with some of the most beautiful scenery you will ever see.
If you would like to see the Napali Coast from the ocean, there are sailing adventures that will take you up that coast and even over to the coral beds near Ni'ihau. If you want to see it from the air, there are some great helicopter adventures that will create some great memories.
Don't let the rainy season (Feb-Mar) put you off, because when it is raining, everything smells like flowers and the waterfalls are flowing at max. If you are wanting peace and a chance to get in touch with nature, you can't beat Kaua'i. If you like trees and flowers, there are three tropical botanical Gardens on Kaua'i (Allerton, McBryde, and Na'Aina Kai Gardens).
If you want to entertain yourself, it is easy to do on Kaua'i.