heres my thought and tips form you:
2 Nights in Paihia - if you want to do a trip to Cape Reinga then def need two nights here.
1 Night in Waitomo - only really the caves here so if your just going to do black water rafting it can be done in 2 hours so you could easily head to rotorua that night
1 Night in Rotorua - not much in the town itself but the polynesian spa is good value also, The Waiotapu Thermal Reserve is worth a visit too.
1 Night in Mt. Ruapehu - I worked in National Park village so it is a great base for doing the Tongariro Crossing plus most hotels run buses to and from the start and finish of the walk.
1 Night in Wellington - Visit the nationa museum of Te Papa its free and good fun
1 Night in Bleinheim
2 Nights in Nelson- i guess your going to visit Abel Tasmen national park from here
1 Nights in Kaikoura - best place in NZ to swim with wild dolpihins but places book up fast so book in advance and be careful it can be cancelled if the weather is bad.
2 Nights in Franz Josef - same again here if weather bad things get cancelled and book in advance, heli hikes meant to be the best but mine got cancelled!
2 Nights in Lake Tekapo - Beautilful place, there is a thermal spa here too also you can day trip from here to Mt Cook national park.
2 Nights in Te Anau - must visit Milford Sound from here its awesome
2 Nights in Invercargill
1 Night in Dunedin - big city good speight brewery tour
1 Night in Christchurch -
1 Night in Auckland[/quote]
Queenstown is worth a visit too