Sorry I missed this earlier.
We've only been to Hawaii twice, so I am hardly an expert. But our DD just informed us that she wants to go to Hawaii for her graduation trip next year (she graduates from high school, and I told her that she could decide our summer trip).
Our first trip to Hawaii was for our honeymoon. We stayed at a timeshare called The Makai Club in Princeville, on Kauai. It was beautiful.
http://www.timesharegateway.com/timeshare-resorts/The-Makai-Club-at-Princeville.html
We were there in September, and I don't remember too much rain. Some of the places we went to included Waimea Canyon, the Fern Grotto, and the Na'Pali coast, which you will recognize from many movies filmed there, including Raiders of the Lost Ark, Jurassic Park, etc. Also the beach where Mitzi Gaynor sang "I'm Gonna Wash That Man Right Outta My Hair" from South Pacific is on Kauai. We also took a helicopter tour, which I loved, but made DH sick. If you go during the winter, you can take a catamaran out and see the whales as they migrate past Kauai. Otherwise, you can still go out and see bottle-nose dolphins and take a snorkel tour.
Our only other trip was about 15 years ago, and we went to Oahu and Maui. On Oahu, the Royal Hawaiian is a nice place to stay. It was the first hotel to open on Waikiki Beach, and is still unmistakable as the "Pink Palace of the Pacific". It is currently undergoing a major renovation, and is scheduled to open January 1, 2009.
We visited Pearl Harbor, climbed Diamond Head, and visited the Dole Plantation. We caught an inter-island flight to Maui, where we stayed at Sheraton on Kaanapali Beach. We spent one day driving the Hana Highway, but mostly just relaxed on the beach - this was after DH ran the Honululu Marathon.
We are thinking about the doing the 7 day NCL Hawaii cruise. My in-laws went on this a few years ago, and really enjoyed it.
Have a great time!