I run out this way for experience on rough tracks and running steps - and there are plenty of the latter on your way out.
This is a Department of Conservation (DoC) maintained track so is generally in very good condition with no muddy stretches and the steps (did I say there were plenty?) are in great order. Your path will go up and down over a few ridges, but the end result is worth it.
This is a 'Kiwi Safe' reserve so NO DOGS (sorry Fido), not even on a leash.
Oh, what is the 'reward'? That will be the great view you won't experience from your car.
The cache will be reachable from the track so you will not have to 'bush-whack' (we are looking after our flora after all).