We had a few days in Auckland several years ago. We went on a trip to Pahia, Bay of Islands, and it was beautiful. We also went to the tip of the island, Cape Moringa ( I think) and that was great - the 90 mile beach was fun and the giant trees - prehistoric ones, salvaged from the swamp were awesome. I forget the exact name of them.
The tip of the island, beach and trees were a day trip which ended with the bus driver serenading us on the way home. A most memorable time, those few days.
Enjoy!