There are quite a few cruise lines that cruise to New Zealand, we have done, Royal Carribean, Princess, Celebrity, doing Cunard next month. Princess will be Australian dollars onboard, whereas Royal Caribbean, Celebrity and Cunard US dollars. I think the main difference between these cruise lines and Viking is there are no casinos on board Viking and I believe child free (not 100% sure), and Viking will be US dollars. Most of the cruises do the Fjords Milford Sound, and normally both the North and South Islands, hope this helps and does not confuse you more.