Raiatea is a very beautiful green island, not much beach if that is what you're after... but it is nice enough to drive around or do the river trip. It makes a nice change from the other Society Islands and with regards to your itinerary it is a good variation sort of. There's a big "marae" Taputapuatea in Oopa on the South East coast which is one of the most "famous" ones in FP and some vanilla market in Uturoa, the main town, but you can see a lot of vanilla too in Taha'a where there are many plantations.
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* with sunshine *