Banana Brain:
I saw a boat load of wonderful recommendations from Iron Chef and others. I also noticed that you may be on somewhat of a budget. So, do not exclude doing some cooking at the beach rental; no doubt, a grill will be there. No fancy restaurant can compete with a home made dinner enjoyed on the beach or by the beach.
If and when you shop for that, get a temporary membership card at Safeway and Foodland and look for the weekly specials for members - you will save a bundle. Keep an eye out for simple but very Hawaiian things like fresh Ahi tuna, try some fresh poke, or "nuke" some laulau. Iron Chef would, no doubt, be more helpful than I on this topic as well.
If all fails, since the new "Go" air service started this month, you will find super bargain rates to come visit our Garden Island of Kauai and we will point you in the right direction.
Aloha from paradise,
Hartwin (Big Kahuna)