Wow I think you guys have pretty much covered most of the places to see.
Well to add some food for thought to this never ending list I've added in places that we loved and would go back to as well which are doable in your time frames (hopefully):
* Pahia - Great fishing get a chartered boat around $80 each and you go away with some awesome fish. You may even see the odd penguin or two. If not you'll hear and smell them!
* Russell - this is a small town but only open during high season really so you'll probably want to bypass this for now
* Tauranga
* Hamilton - Do the glow worm caves at night. There are free ones if you take the car out past the main hotel. Again info centre will give you directions. Take a few torches and off you go. It's great fun. About a 25min roudn trip.
You can also do sheep sheering there as well! Not tried that yet.
* Rotorua - wander round some of the free parks and get a wiff of egg. Great way to get a feel for the traditional NZ even if it is touristy. They also have the best pie shop just on the turnoff to the Aquatic centre.
* Taupo - Go to the info centre and they'll tell you what road to go up to see the free hot pools. I cant remember the name of it but it's 3mins by car from the city centre. Great sceneray just sitting there bathing away. And free of course.
*Napier - visit the Marineland there - I loved it, probably the biggest marineland I've seen.
* Martinborough - Great for the adults not to sure about the kids tho. There are glow worm caves there as well. Info centre will give you a map. be prepared to walk through hip deep waters!! This is only a wee cave and you only see a few glow worms but worth it for clambering about for 5 mins in the dark in water! Take a few torches.
*Woodville - Stop in at Yummy mummy's cheesecake shop. To die for cakes in there. Stock up as they dont yet do internet orders LOL
* Wellington - Tepapa museum, free entry. Go up the cable car. Great views. Enjoy a stroll along Oriental Bay and stop in at a few cafes. Not really anywhere you should avoid. I would say pop in but we dont know where we're going to stay when we come back from our holidays in Aug
South Island
* Kaikoura - do the sea whale trip rather than the air one but remember those sea sickness tablets.
* Franz Josef - Gotta see the glaciers, you can do a small walk for free to see the bottom on the glaciers or an organised trip. We did an 8min snow landing for around $100+ each and landed on the glacier. This was something so unreal.
*Wanaka - great lake area. You can get the kayaks and kayak out to the wee island. Great place to chill out before decending on Queenstown.
*Queenstown - Do the icebar, kids as well. Luge. Mind you this isnt as good as the one in Rotorua. Loads of activity sports to do down there. We stayed in a holiday park next to the indoor mini golf. Another most. Best mini golf in the world I think
I've probably missed out heaps more to do but will add them in when I remember.
Most of all HAVE FUN on your travels. They go in way too fast!!!