Just replying to cdw, the honeymoon couple. Central North Island is some what tropical compared to the south, so rafting and kayaking operaters are open all year round in this area. check out www.kaitiaki.co.nz
, rafting and sledging company in Rotorua. If your partner is not up to kayaking these rivers, then i highly recomend she takes the sledge option with Kaitiaki, she will absolutely love it. Also my partner owns the company so i can vouch for their professionalism. There could be a surprise by June, a section of river most beautiful and untapped at present, Kaitiaki may be operating this section by then, if so, wow!!!!!! Also Sunspots Kayaks are open, Donald Calder makes a brilliant kayak guide.
Australia, worked up in Cairns in my early rafting days, all good too, its just not New Zealand, hard to compare. Id love to take you both kayaking, but june july ill be in your part of the world.
sweet, hope that helps