Hi, 3 couple are driving in a rented mini van from Auckland to Lake Taupo and then on to Rotorua. We have hotels booked in Taupo and Rotorua. What are must see sights along the way, good place for lunches etc.

To be honest there's not much to see between Auckland and Rotorua. You can stop off in Hamilton for lunch but it's not a very exciting city and my advice would be to bypass it. The Mamaku ranges just before you get to Rotorua are nice and a good spot to have a picnic but by that point you'll be so close to Rotorua you may as well just go all the way and spend all your time exploring the hot pools and other attractions of Rotorua.

Typically people detour to see the glowworm caves at Waitomo.

Thank you for this information... Perhaps we should spend half a day in Auckland before heading to Taupo. How long of a drive is Taupo?

It takes about 4 hours at an easy pace to get from Auckland to Taupo, direct.

The suggestion of going via Waitomo is a good one (Bit longer than direct of course).

You could stop off at the Otorohanga Kiwi house on the way.

http://www.kiwihouse.org.nz/

There are country cafes in most small towns along the way. Varying quality of course but usually reasonably edible food.

A half day in Auckland would not give you much unless you were just after a bit of driving round up a few of the volcanic cones here in the city or maybe a quick trip up to the museum. Auckland can be a bit of a mission to commute around at peak times (Which I would assume would be when you were looking at travelling, morning peak time).

If you allow a longer time to look around the city with no pressure of being anywhere there are many great sights in the city.

Check out

http://www.aucklandnz.com/

I hope this helps

Heres my things to do in the area.
Rotorua - to see the geysers, thermal activity and smell, visit Te Whakawerwera for your Maori cultural experience.

Drive out to Lake Tarawera near Rotorua- check out the Blue and Green lakes on the way

Taupo- Tandem Skydive 12,000ft

Craters of the moon outside of Taupo

Tongariro Crossing- one of the best one-day walks in the world, stunning scenery with volcanoes

Top things to do in New Zealand
http://www.newzealandatoz.com/index.php?pageid=227

Two suggestions for your Auckland to Rotorua leg. Firstly have a break at the gardens in Hamilton - we're not mad keen gardeners but thought the gardens were lovely and there is a nice cafe overlooking a small lake.
Secondly, we had a very pleasant dinner in Rotorua. There is a gondola to a restaurant on one of the peaks around the lake - sorry I can't remember the names but I'm sure someone in Rotorua will tell you. Apart from nice food, there are good views across the lake and the town.