I think renting a car for a day on either Bora Bora or Moorea is a great idea. It is fairly easy either place. We rented on Bora Bora - there was a rental site right near where the boat drops you off. In Moorea, I remember people right where the tenders drop you off to rent cars from. Be prepared to spend around $60+ for the rental.

Bill

Paul Gauguin 3/06
Navigator 11/04 (Caribbean)
Paul Gauguin 2/04
Mariner 7/03 (Alaska)