Whangarei is a new cruise port, our home town, not sure what will be in place for cruisers.
If there is a shuttle into the city, the waterfront is nice to look around, can walk the hatea loop around the waterfront. Can walk to the shops in town, not a lot to see there. Rose gardens close by to town.
Hunterwasser museum maybe worth a vist in town basin (waterfront) unusual building to look at from outside. Hope this helps