Find Your Cruise
All the tourist bits accept the yankee dollar. You'll need to check with the shop/cafe/etc in non-touristy bits, like Porlamar on Isla Margarita....and Caracas, which is not geared for tourists, but if you go on an organised tour (Caracas is the only place where this is strongly recommended) the guides tend to help out with "small change" for a beer or a souvenir.
In the unlikely event that you want to buy something expensive almost all the larger shops accept visa/mastercard.
As always, take plenty of low-denomination notes (or change down from larger notes at reception on OV2, no charge), because you will probably be given change in local currency. Have a great cruise, Chris.