I do not know if you have any choice of hotels before your cruise, but I personally would check if instead of Tahiti you could spend your days in Moorea. It is just a ten minute flight away from Tahiti, so you would not loose much time from hopping on the other island.
I have actually found Moorea more interesting and scenic than Bora Bora - as an island. If you include the lagoon and the motus into the picture Bora Bora wins hands down.