The trail is a well formed flat metalled path for 90% of the walk. If it wasn't for the first 50 m you would probably get a wheel chair along it.
This is one if the many entries to the forest park and if you are keen to explore more you could stay at the basic camp site (toilet only) which is close to the cache.
Might also be worth bringing a torch as there is a limestone cave a little further up the track that you can scramble through. There is usually ankle deep water/mud in there but the kids will love it!
For the fitter ones there is also a track to the tallest native tree in NZ (66.5m high) but you can expect to add another 4 hours to your journey if decide to visit it - worth it for the novelty/trivia value?
The cache is a 2 litre camo painted Sistema box containing a logbook, pencil, stashnote and a bunch of trading goodies. There is medium tree cover at the cache site but my 60CSx had a 5.2 m EPE when the cache was hidden. No need to bush bash as the hiding place is only one step off trail. Just in case some of the older GPSr's struggle there is a very detailed encrypted hint to minimise the chance of a DNF.
Oh - did I mention the swing bridge? EDIT: Swingbridge replaced by a wide solid wooden bridge in 2009.