I would suggest getting some Tahitian money if you plan to do activities other than the excursions. The last time we were there for example, Albert's would only take Tahitian money when renting his scooters. Also, for gifts, some of the out of the way places/small shops may only take Tahitian dollars. We actually found pareos on Bora Bora that were actually made right there on the spot by the locals (most of the ones in the Papeete market are not made in Tahiti) during a tour with one of the local guides. It was only $10 (US). A pareo with one of the books showing you how to wear them made nice presents. There is also alot of local shell jewlry sold on ship or at the ports that make nice gifts at very reasonable prices. I know you will have a wonderful time on your cruise and the gorgeous islands. Wish I were going with you!!
Sally