Check over in the celebrity threads for a similar question, Chuck Palm has made several really good recommendations.
I did not realize you would be on the island for a week. For a nice lunch or dinner and a nice scenic ride, drive around to the east coast and try the Crouching Lion .
If you are there for a week, another must do would be the Polynesian Cultural Center.
Plan to spend all day and into the evening. You get there at noon for opening and stay till about 10pm. Book the Ambassador package which is well worth it. Gets you an all day , small group private escorted tour. In addition it includes the Luau for dinner, the extravagant show spectacular after dinner in the show stadium, videos, leis, programs and deserts at the after dinner show.