Being by the ocean really does make it better. The food is decent, and the drinks are pretty good for being served in small plastic cups. But the people are quite friendly, and the sight and sound of the ocean creates an unmatched ambiance. If you are willing to spend the extra money, consider getting the premium option, where you can skip the very long lines, sit in front, and can eat on real plates.
The luau will call to confirm only a few days before the reservation, so don't worry if you don't hear from them until you are already in Kauai.