I recently got back from a trip to NZ, OZ and Fiji. Ive been to both the north and south islands of NZ and my advice would be the south island for sure! There is soooooo much to do there! Here is a list of stuff i did and would gladly give you more info if you want
nelson-sky diving and mountain biking
Christchurch-awesome city, nightlife!
Queenstown- must do thrilogy bungy! shot over boats, para-bungy!
Mt. Cook- mountaineering, skiing, glacier boat tour (rad!), fishing, hiking
Wanaka- rock climbing
Route burn track- you say you dont like hikes? neither did i until i did this one!
Fox Glacier- glacier hike, and ice climbing
I did a lot more, but these were the best! The south island is where its at! The scenery is also gorgeous!
hope this helps, if you need more info let me know!