Kauai: Hanalei Bay | Kilaeua Hawaii Hikes | Trails.com
I know you can't see much without registering, but I'm quite sure this is the one I did and it was awesome.
It's not far from where you'll be staying although I'm not sure if you can get there without having to go around the whole island.
Pat's Taqueria, just a small but popular taco stand, near the pier in Hanalei is run by my cousin's partner (if they are still together) and is bitchin good.
Hawaii in general is supposed to be a breeze, but I've only done it yuppie style when I was like 14.
Have fun!
-Christopher