If you had looked on their web site you would have found the following. - What is the currency on board and how do I pay for items I buy?
Currency on board all ships is the US dollar, and you'll find the Purser's Office acts as a handy financial centre. You don’t need to take cash, as all shipboard purchases are charged to your on-board account. You can settle your account by credit card or using traveller’s cheques. To make life easier, we recommend you register your credit card at embarkation. You can exchange cash and traveller’s cheques at the Purser’s Office for most currencies in use at ports of call. Please note that personal cheques cannot be cashed on board our ships.
New Zealand Dollars.
I am flying into London and Traveling on the Queen Mary 2 to the British Isles. What Currency should I bring?