Dd is 13 months. I moved here 7 years ago on my own (actually just came for a year's working holiday and ended up staying). Met dh here (he is English too). I had a good few years of being here before having dd so I had plenty of time to go out socialising, met people through work etc.
Plus points, it is a lovely country and has lots to offer. Of course, it is not a paradise and has crime, poverty etc like anywhere. But on a day like this, when I just wandered across the road and down a path to the beach where dd paddled in the sea, I can see all the good stuff.
I actually wasn't really homesick till I had dd and I have found it hard being away from family since she was born, sorry, I'm not much help there!
I think it's a good idea to think, well you can go back in 3-4 years, there is always that option. And if/when you do go back, you can look back in years to come and know you gave it a go and weren't always wondering what if. It's great your family are so supportive and will visit.
OK your worries:
Making new friends - Kiwis are generally v friendly though I know people in some bits of Auckland have found it hard to break into established "groups". I found it a bit hard after dd was born but mainly because none of my friends have had kids yet so are all still doing the going out every weekend thing. I have met some lovely new people now through playgroups, music groups etc. Do you know whereabouts in Auckland you'll be livign?
Managing being so far away - it can be tough but I haven't known any different really. Do you have a lot of family support in UK with the dcs? For keeping in touch Skype is great as it really makes a difference seeign people on the screen as well as hearing them.
DH job - what work does he do? Unemployment is pretty low in NZ and, so far, the recession doesn't seemed to have kicked in too much.
I worked for 6 years in a childcare centre so can answer questions about that if you want.
I assume you have checked out www.trademe.co.nz and www.realestate.co.nz/ for property and www.seek.co.nz/ for jobs.
Hm, can'[t think what else to put at mo. Auckland has a lot of lovely bits, it can seem like a bit of a sprawl but there are fab bits around and nearby, the Waitakere ranges (near me!) the West Coast beaches, North Shore beaches, Clevedon, Kawakawa Bay, Whitford and surrounding countryside, the harbour on a lovely sunny day, Waiheke island, all the islands really - I could waffle on but you get the picture! Sometimes you have to drive aorund a bit to find the lovely bits is what I'm getting at!