Another target that you might want to consider which would make a fantastic 2-3 day trip at the end of the year is Mt Brewster. We did it a few months ago and it was probably too dry (the summit ridge is particularly chossy for NZ standards) but in December is might still have a bit of ice to stick it together. There is a nice flat crevassed glacier, the summit west ridge has a couple of rock steps (one short pitch of grade 8-10) and you walk up from the road so you get to experience the full NZ backcountry beauty. There is also a very modern hut to stay in beneath Mt Armstrong if you get caught out with the weather, although we camped near the toe of the glacier which was glorious. Perhaps you could use it as a training trip to work out glacier technique with you buddy without significant exposure to the elements (Quarterdeck is quite steep and Bonar is prone to whiteout - trust me). The views from the summit are bloody good. I am sure there are people on this forum that would consider Brewster a doddle but I think it will provide a nice test of route finding and decision making.