My wife and I are Maui fanatics (going again next year). I'd like to offer you some potentially cost and headache-saving advice: unless you're using points or are only on Maui for a long weekend, your best bet is almost always to rent a condo instead of fiddling with hotel resorts. When we go to Maui, we use a travel agent who lives on Maui who sets us up in a condo with full amenities (kitchen, washer/dryer, wifi, ocean front, etc) and none of the nonsense found at the hotels, such as "resort fees", "parking fees", etc. When you arrive at Maui make your first stop the Costco (conveniently near the airport) and load up on food, adult beverages if you wish, and other goodies.

As far as places to visit, I highly recommend you visit TripAdvisor and look through the listings of highly rated, and diverse activities. My wife and I are in our 50s and not really into things like scuba diving or ziplines, so we go for other things like sunset catamaran cruises, a trip to Haleakala crater, etc. There's also the ever-famous "road to Hana", which is a twisty-turny heck of a drive but extremely beautiful. Our travel agent (who lives on Maui) advised us that it's best to just drive to the halfway point and turn around (there's a banana bread stand there), because the rest of the drive is about the same and the return is very exhausting. For dinners out, there are three places you must do: Haile Maile General Store, Mama's Fish House, and Nick's Fish Market. If you'd like the contact information for our travel agent, contact me privately as I don't want to be accused of spamming the forum. :-)