If you have a week or more on Maui, you may want to set aside a day or two for a trip to Molokai or Lanai. Tour operators such as Trilogy offer day-trip packages to Lanai, which include snorkeling and a van tour of the island. Ferries are available to both islands and have room for your golf clubs and mountain bike. (The Molokai channel can be rough, so avoid ferry travel on a blustery day.)
If you prefer to travel to Molokai or Lanai by air, and you're not averse to flying on smaller, propeller planes, book with Mokulele Airlines for flights to Hana, Maui, and Molokai, or with Island Air for flights to Lanai (via Honolulu).