Well for snorkeling you'll probably want to check out the
Molokini Crater. It's a very popular place to go snorkeling. There's also the Olowalu Turtle Reef.
As far as seeing the sunrise from a volcano, you'd probably want to head to the
Haleakala Crater. Since it's so close to the new year, you may not be able to get a cabin but they do offer campgrounds.
Spending New Year's...check out the Kaanapali Beach Hotel, known as Maui's "most Hawaiian hotel". Reservations are a must so be sure to call in and check out the festivities they have lined up at the
Kaanapali Beach Hotel.
Hope you enjoy your trip....let me know if you have anymore questions.