Thank you Mwenenzi, didn't know about the NZeTA (this trip is in a couple of months, so sorting it all out now) - that's really helpful to know.

If the CX flight is really delayed (from its history, it seems ok - and Cathay are pretty reliable, but still..) - then I'll have to find another way to PPT, and we'll stay with a friend in Auckland instead. Would be a bit of a disaster for the first part of our trip, but I know (from past experience) that such things can happen (even connecting flights on the same ticket before), so would just have to deal with it! Or buy a boat...