Erasmus, if you have any AA miles, then you can use car and hotel awards to redeem for a hotel in Auckland.

40,000 SPG = 50,000 AA

There are a few 3 and 4 star hotels available around that price range. Not sure that I would want to spend 5 nights in Auckland, though... Personally, I'd leave Auckland and go up to Bay of Islands, or drive down to Rotorua, etc...

Best to ask in the Australia, New Zealand & South Pacific forum for suggestions.