Don't do it January if you can. Feb and March are much more reliable if the last few seasons were anything to go by.
Oh yeh, expat kiwi here. Chur chur!
We've done January the last couple of years just because it's normally easier to swing leave from work then (as you know, the whole country here basically shuts down for a month over Jan!). March is probably a bit late but Feb could be an option - any major holiday peaks to avoid there?