Auckland to Christchurch. Suggested routes?

I'd pick Rotorua, It's a very touristy city, but has much closer access to the thermal parks and Maori culture.. Taupo is pleasant, nut, to me, didn't really have much to make me want to stick around. Wai-o-tapu is a great thermal park, Te Papa geyser, the public gardens, spas and thermal pools. I also really liked the Redwood forest on the edge of the city.
Kids will love the gondola and especially luge ride just outside the city.
From Napier there's really only one route you can take, unless you double back to Taupo.
There's a lot in this which doesn't make sense to me.
In 10 days I wouldn't be wasting a single day in Auckland, Napier or Christchurch. The most spectacular parts of NZ are Mt Cook and Queenstown on the south island. If possible, I'd be skipping Napier, and trying to drive through to Mt Cook, skipping Christchurch.
But if you do go to Christchurch see the Antarctic centre. Akaroa, about 90 mins south is a gorgeous town.

Thank you for your input.

We have a family wedding in Auckland, so we fly in late friday and head to our next destination on Sunday,

The trip in itself is a bonus, so anything we see will be fantastic.

I am considering bypassing Napier to spend more time elsewhere.

I am meeting a friend in Christchurch, so we plan to spend at least a day with them :)

That all makes a lot more sense!
Rotorua is interesting, and will offer a lot to kids by way of rides, thermal parks, and perhaps a soak in the hot pools. Our kids loved all this. However, the sulphur smell pervades everything and takes a bit of getting used to.
Taupo is a pleasant, scenic location, and not far from Rotorua, and some of the thermal parks are about a 1/3 the way from Rotorua to Taupo, so you could end up there. There's a great hot springs park with accommodation called Taupo De Bretts, which kids would enjoy.
Hobbiton, near Matamata, the actual film set for Hobbition in The Hobbit and Lord of the Rings was also fun.
We diverted out to Coromandel, instead of Napier, and saw cathedral Cove and Hot Water Beach, which we enjoyed.
From Picton you could head straight down to Kaikoura and see the dolphins, see Akaroa, and stop off at the Antarctic Centre, which is right next to the Airport.
Christchurch also has a gondol and luge ride.
Ou holiday snaps can be found here https://plus.google.com/photos/103601112150543876314/albums?banner=pwa

I suggest you use Highway 1 on the day you travel to Wellington. Driving along the seaside at Pukerua Bay is one of my favourite indulgences.

Try to arrive at Wellington in daylight. As you emerge from the Ngauranga Gorge, Wellington is suddenly there before you. Amazing. Wellington is well worth a day - or more! I've lived there for 16 years and still enjoy every day.

I'm a kiwi. The drive down the middle beyond Taupo is the most boring drive in the world. I do it only because it's the most direct if u r travelling to Wellington. As a tourist I suggest you do Rotorua , taupo then over to Napier and down the east coast. There's lots of cool little places and in Martinborough some cool cafés and good wine.. Just don't go down the middle.