Ioarana! The island greeting.
Oh dear, where to begin, the French Polynesia was a place I loved to visit when we would go on extreme fishing expidition(s). To answer your question is like asking which island should I visit in Hawai'i. It is going to depend on finances, time, and the ability to want to suck in every bit of the island you choose. Being that we are talking about Tahiti, the place known as Pape'ete is where you'll land. This is your higher end things of the trip. That island is seperated by a small village Taroava, or Tarova, something like that. It's kind of shape like Maui, Hawaii, so where the narrowest part of the island is what seperates Nui, from Iti, big and small. In the big part of Tahiti I enjoyed Tiarei, and Waterfalls town. On the smaller part of Tahiti, you have the must see Teahupuo, (pronounced: chi-oh-poh), a surfers paradise. Other than that, you're pretty much in Tahiti, what to enjoy is literally every edge of the island. Prestine waters and warm beaches. However, Overlook is a nice place to view the landscape of Iti.
My money, however, went to the island of Raiatea...no words Karen, just bliss.
I'm jealous you're going, be sure to upload the pics on the awesome Hub I'm sure will come from this lovely visit to French Polynesia.