I agree with comments by rjsk23 about the consideration and care taken by Princess for passengers with mobility concerns. Harry travels with a small mobility scooter, which at home we fold up and fit into the boot of the car. On a cruise it allows us to roll on and roll off without worrying about booking it through baggage handlers as you must do when travelling by plane. It also makes getting around the ship easy - the distances are surprisingly long for people with mobility problems.
This was our fifth cruise with Princess and on each occasion we have been impressed with the service and care. On this cruise our cabin steward was particularly helpful and anticipated needs and helpfull extras - for example a blanket for an afternoon nap and a door stop to make getting in and out of the cabin easier. Those doors are heavily weighted.
The Shore Excursions Desk was as always helpful with advice on whether we should take the scooter ashore or use one of the wheelchairs available on board for shore excursions - wheelchairs are easier to manage on rough or sandy terrain, provided the pusher has the strength.
We always book a balcony cabin close to the lift well in case of bad weather and prefer to eat lunch on the deck where it is easier to park the scooter instead of in the Horizon Court itself. In the dining room there is always a waiter willing to provide valet parking for the scooter.
New Zealand itself is well set up for people using wheelchairs and scooters. Buses with ramps and special seating areas are clearly marked and resonably frequent. We booked several tours and activities through the internet and everything we organised worked including special arrangements at Speights Brewery and the Sky Tower and a car with a larger boot in Tauranga.