Looks like a great rideAlthough I'm not sure about the 'moderate' hills in the South Island
If you had a chance, the Central Otago Rail trail is a great off road ride from Clyde to Middlemarch, it's a fantastic ride.
Personally (probably because I lived in Auckland) I'd have spend some dirt time in Rotorua as its the best -rather than Auckland. But you do have friends there, so you could always rent a bike and go to Woodhill Sands mountain bike park or if you prefer road, head out to south Auckland and cycle the coast from Whitford to Clevedon.
Enjoy !