Well said, Explorer. I'm from the island of Kauai, and unfortunately there are no gay bars or clubs. Most gay people hang out at Donkey Beach and also the beach at Lydgate park. And as Explorer said, many gays do dinner/cocktail parties.
The islands are pretty gay friendly and there are a lot of fun things to do and see. On Kauai, go to Waimea canyon, take a boat ride up the Wailua river, take a helicopter or zodiac ride around the island and witness the beauty of the Na Pali coastline.
I think it's also worth exploring the grounds of the major hotels. They are so beautifully maintained and very romantic. Have cocktails at the Hyatt Regency in Koloa, lunch at the Sheraton Princeville (absolutely fabulous!) or hang out at Kalapaki beach at the Mariott Hotel.
Explorer also gave some great advice for Honolulu too. Hula's is really fun and so is Queen's surf. I'd also recommend Mai Tai's at sunset at the Royal Hawaiian Hotel. You can experience the torch lighting ceremony and a beautiful Hawaiian sunset at the Mai Tai bar, where Mai Tai's were invented. (not to mention all of the gorgeous surfers returning from a day out on the waves.)
Being that you'll be there during the winter season, you may experience some rain, but it is still very beautiful.
Have a great time. - Jorel