We loved our trip to Maui, but it was too short. There is so much to see and do that it is hard to choose things. Plan ahead if you can on the most important things you want to do. The guys wanted to snorkel alot and we girls wanted to shop. Hana was a must, but if you suffer from motion sickness, take something.I was told to take Hawaiian ginger and it helped.
If you want a more authentic luau, stay away from some of the hotel ones put on (too hokey). Watch out for the timeshare traps. There are discount booths all over the island and will offer you stuff in return for some of your time. If you don't mind losing an hour or so some of the discounters offer a good deal on snorkel cruises. If you plan on bringing pineapple home, call Take Home Maui - they deliver right to the airport and prices were good. Look for their coupon in one of the booklets at the airport.