Waikoloa is pretty amazing! I love the Hilton there actually, like 9 pools, including sandy bottom ones for the kids. A natural lagoon with turtles always hanging out. Like 60 acres, you can ride the boat, tram or walk between buildings that have all kinds of Ming Dynasty art work that were put into the hotel when it was built.

Do the night Manta Ray dive right off the coast there (although you depart in Kona Harbor), and I've done it as a night dive and snorkel and prefer the snorkel as the manta come from the depths and scoop up the krill that are attracted by the light arrays the tour companies lie on the sea floor. The dive you end up looking up the whole time which I found uncomfortable. On the snorkel your in perfect position to see the action.