White water rafting is pretty much available anywhere in NZ, so that won't be a problem. Come to think of it, bungee jumping is too. I guess I was really building up to pointing out that if you are an adrenaline junkie then Queenstown is where you want to be for a while.
Have a look at [broken link removed] which is the website for the main chain of campsites. We found them to be OK, but some of the non-chain ones had more character. Having said that, if somewhere has a Top 10, then it has to feature at least some significant tourist facilities so their map is a good place to start. If you do go Top 10, get their discount card as it saves you 10% off every night and pays for itself in a few days.
Also, you will not be able to do much of both Islands in the period you have available unless you spend most of it driving.
It takes 2 days (or one very long one) to get from Christchurch to Invercargill and another 3 to get back up the west coast to the ferry to the North island. And that's without spending any time seeing anything.
Wellington to Auckland (or Bay of Plenty) is another *very* long day or realistically 2 days and even then you haven't seen anything on the way.
Maybe you could say where you fly in to and where you fly out of, that would help.
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