Hmm. Since my favorite luau are on the island of Maui, I don't really have a strong opinion on this. I think Dean has given some very good advice, and Girlimama33 has a nice suggestion for your luau.
I think that since you will be at Aulani for a week, Pardise Cove would be awfully convenient. It's almost next door to Aulani. You want to see as much of Hawaii as possible while you're there, so I say when choosing a luau, as Dean suggests make it EASY and convenient! Oh, and don't miss the Starlit Hui at Aulani! It's free, not really a luau, but gorgeous dancers, some great history of Hawaii woven in, and one of my very favorite Hawaiian musicians, Keali'i Reichel, helped put it together as well as wrote the chant for Aulani that you will hear playing throughout the resort!