In December and January I spent 3 weeks on the South Island of New Zealand with my husband and 2 daughters. It was a fantastic place with so much to do and the most awesome scenery. It was like driving through a picture book. The lakes down through the centre of the island are aqua / turquoise in colour and the mountains are simply awesome. The activites on offer are enormous with Queenstown having something for everyone, from the Steam boat across the lake, the the helipcopter flights, Luge, Jetboat riding, white water rafting, kayaking, walking trails, quad biking, horse riding, day trips, I could go on and on. Leaving Queenstown we went up the West Coast to the Fox and Franz Josef Glacier where on a good day you can take a flight and land on the glacier. Again truly inspiring scenery. I would recommend the South island to families, couples of any age as there is something to see and do for everyone including a visit to Puzzling World in Wanaka which was great fun getting lost in the 2 storey Maze.
I would say Take care whilst driving as the roads are narrow and very winding along the West Coast and if rains a lot! there are heaps of motorhomes out on the road and everyone we met during our travels were helpful. Christchurch is really beautiful with some great local attractions.