The guys have covered it pretty well. The drive up to Kokee is worthwhile, check out the canyon, go to the lookouts over the Na Pali up there.
Driving toward Lihue from the south there is a neat bypass near the animal shelter that gets you off the main road on your way to the harbor, nice scenery.
I'm a north shore guy and would suggest you spend some time up that way. The views from the lighthouse are good. Lots of sea birds nesting on the craters edge nearby.
Anini Bch and Kalihiwai bay are a little off the beaten track and nice. Some good sheltered snorkeling at Anini.
On your way toward the end of the road and the beginning of the Na Pali coast trail. (Should hike in to the first good view point, 20 min, best in the early morning.)
You will go by limahuli valley, nice botanical garden there featuring native plants and restored taro terraces .
Tunnels beach gets crowded but is beautiful and nice for a snorkel .
The ahi at the dolphin restaurant in Hanalei is killer, they have a little shop in the back where you can pick up some nice poki, sushi, etc for your lunch while exploring the area.
Kayaking up the Hanalei river and in the bay is good too.
Have fun,
Cheers Richard
