Great time of year to go, two summers in a row will be a great way to start your new life!
Agree totally with other comments re public transport, I understand it is somewhat better than it was when we left 8yrs ago but it really is PANTS compared to the UK. When I was home for a visit a few yrs ago a 20min car journey was going to take me over an hour and half and 2 bus changes!! Its likely you'll need to be a 2 car family but with some organising one car will suffice.
Lots of great suburbs in Auckland but just like anywhere some you probably would want to avoid. Has your DH got a job lined up? Best to figure out where he is located and work back from there, Auckland motorway in peak hour traffic is a bit of a nightmare!!!
From a 'setting up new life' point of view as I said in another thread in this section, give yourselves loads of time to settle in. While lots of parts of NZ life will feel strangely familiar its not home and you are likely to get homesick. Try not to dwell on the frustrating / negative parts of life and plan regular interesting events / holidays / trips etc to help you keep enthused about your new surroundings. I'd say expect a 6 to 12 mth time frame for adjusting and feeling more settled, might be quicker with kids and getting involved with school, sport etc
It is rather expensive to go to the Dr in NZ compared to here, its subsidised but still around $40 / $50 for an adult, so if you are at the Dr regularly then you might consider Private Medical Insurance (Southern Cross, Tower Ins, Sovereign were are few of the big companies from memory), you DH might get cover through is work tho.
Best of luck for your new adventure!!