We just stayed at the Mauna Kea and absolutely loved it. It was a fabulous experience. We had a room with an incredible view of the ocean.
We went to the Luau which was a lot of fun here. The food wasn't fabulous so I would recommend just buying tickets to the show, which is what we did, and then eating at the Manta post. The Manta has the most incredible setting and divine food. We also ate at Monnettes which was good but not as special as the Manta.
I would highly recommend dining at the Canoe House as well. I had the Mahi Mahi which was spectacular and the the outside view at sunset was unforgettable.
I would also recommend hitting the Four Seasons for dinner. The restaurants and setting there are remarkable.