I'd also do one island if you want to relax. Losing half a day or more to interisland travel/check in new hotel just isn't worth it IMO.

I also recommend those Revealed books. Pick whichever island you're interested in, and then get the Revealed book for it. Totally worth the small investment. Search online for Borders coupons if you don't have time to order them online. I've gotten a few other Hawaii travel books, but the Revealed ones were the best by far.

Sunrise on Maui at the volcano requires you to (usually) leave your hotel/condo at like 3am in the morning. It's also freezing cold so you need to specially pack cold weather clothes that you'll only use for that event. Not sure if it's worth it. Sunset at a beach is just as romantic IMO and a lot easier to get to (from my balcony at my condo on our last trip).

I like Honolulu. Sure it's like a big city, but there's lots to do. You can get some tropical paradise feel outside Honolulu in other parts of Oahu. For a first timer, Oahu is my recommendation.

Second place would be Kuaui. Never been there, but it's the favorite for quite a few of my friends. They've shown me pics. That's the tropical paradise lots of people imagine Hawaii to be. Not much to do event wise, but if you want to relax, frolic on the beach, or check out beautiful nature, it's the place to go.

Maui, while it's often billed as a cross btw the hustle and bustle of Oahu and the serene beauty of Kuaui, is more like the worst of both islands instead of the best IMO. Not much "city" our "touristy" stuff there, and what's there is quite poor compared to Oahu. The nature scenery isn't anywhere close to being as beautiful as Kuaui.

Hawaii, the Big Island, looks like it has more "stuff" to do based on my research, but everyone I've talked to, including a person who grew up there, has it last on their list of islands to see.