Our experience.
It can be very easy to just see the good side of things when going somewhere new. Try hard to spot the things that will niggle you and whether you can live with them. They are different for all of us and they will depend on your own values.
It may be something really small - but beware of small things - or something that is a huge issue to you. New Zealand has a different culture and those of us from the UK have to take care that we don't presume it is just the UK on the other side of the world.
I think we maybe felt that to a certain extent during our previous holidays, until we started to look seriously at a life out there during our visits last year. We have a trip planned next July where it really will be a final - 'can we live here trip'. (I'm sure the answer will be yes
)
Above all enjoy yourselves - the kids will be fine - they will be more than fine staying with mum-in-law, they will get spoilt rotten.