Are you staying at the Princeville resort on Kauai? I stayed there back in '95. If you keep going north out past the wet caves to the end of the road, there's a hiking trail with some spectacular views. You can hike about 9 miles out to a beach on the other side of the island. I didn't do it, but I've heard from others that it can be cool.
Trivia: On Kauai on the road between Kapaa and Princeville, you'll go by a valley on the western side of the road with a plantation at the bottom. It's a big drop-off. Douglas Kenney, one of the co-writers of Caddyshack (among other things), either fell or jumped to his death there. So, y'know, be careful.
Congrats!