In reply to all:
Wow - you go away for the weekend, and look what happens.
Thanks for the advice, everyone.
Jam - yes, I've heard that river wading seems to be a feature of NZ tramping, whether it's intentional or not.. (heavy rain, rapid river rises).. hence the question in the first place.
Yes, I know the Tongariro is the equivalent of going up Snowdon, but there's still something about it that appeals to me.
Milford - much as we'd like to get down to the lakes, I don't think our schedule will allow it. I also think it's the least likely place we're likely to find peace and solitude in NZ!
We'd chosen the Queen Charlotte for two reasons - a) the water taxis take your bags, and b) you get to stay in hostels along the way, rather than bunk huts. Call me a wuss if you like, but at the end of the day this is our Honeymoon as well, and spending it with 50 strangers in a bunk bed wasn't really what I had in mind...