My wife and I went to La Mer as a part of our honeymoon and we absolutely enjoyed it! This is the most romantic restaurant I have enver been to. We had a table, oceanfront with an open venician style door so we can hear the waves and fully appreciate the sunset while eating our 10 courses "menu degustation".
I do not know if you taked your decision already, but you ( or they) should consider this place for their perfect honeymoon diner! The only "negative" thing about this place is the price for sure ( It cost us more thant 400$ with taxes and services) but we felt the food, drinks and service we had there surely worth the money.
At this time ( may 2007) It was the only 5 diamonds restaurant in all Hawaiian Islands and it is located inside the Halekulani Hotel, which also include Orchids restaurant wich seemed also really nice especially the location, but I don't think you can compare both for the food and service.
I hope these informations will help you. You can also go to their website if you want more infos...