It's been a while since I played tourist on Maui. Some things that I would recommend are:
Go to the top of Haleakala (You can look over the Alenuihaha Channel and wave to Poi)
Visit the Sugar Mill Museum in Puunene (disclaimer: my first trip to Maui was to do of-fseason maintenance in the sugar mill; so I might find that more interesting than some people.)
Ride the Sugarcane train in Lahaina
Visit the Whalers Village Museum in Lahaina
Maui Tropical Plantation is interesting (as I recall).
I would be sure and spend some time in Kahului at the Queen Kaahumanu Center. I like it because it is less "touristy" than the mall in Lahaina.
Have fun.. and be glad your vacation wasn't 10 days earlier. The weather has been pretty stormy in the islands with high winds and flooding last week. Oh, BTW, don't read "Airframe" by Michael Crichton on the flight out here either. If you really wanted to try out Alistair MacLean though, I'd recommend "When Eight Bells Toll" for your flight out. It's my favorite.