Thanks everyone for your excellent advice, especially drvalgemae who basically gave me a Lanai-for-dummies crash course on where to go and what to do. I wouldn't have been able to pull it together without your help. Mahalo! :)
Link to my blog: …blogspot.com/2013/02/day-8-daytrip-to-islan…
We flew in from Oahu in the morning and left on the last ferry to Lahaina, so we had to make some difficult choices (had to skip the Munroe trail), but we were able to get a good first impression. Garden of the Gods was amazing and I loved the Shipwreck Beach area -- and let's not forget driving the Hummer; that was quite the adventure. Lunch at the Blue Ginger was perfect btw!
It's a bit quiet for me so I wouldn't stay for a week, but I'm not ruling out another daytrip in the future.