If you need any more details of things to do when there give me a yell. I do know that cruising in your own boat is Mega expensive with lots of red tape. I don't know if this matters to you or not. The best way is to book onto an organized cruise. That way you get to see all of the islands and with a decent guide to boot. They also offer diving etc.
Be careful though as i have a horror story lol. I booked onto a 3 day cruise which was out of this world. Best time of my life. I did however manage to catch....ahem.... scabies from my bunk. I think the crew were using it when we were ashore grrr. The worst of it is, i didn't realize i'd caught it until after we'd set off for the Marquesas. 17 days of pure hell!!!
You don't even want to know what happened after the Marquesas!!!!!! Horror story!