Tony wrote:planning to do the Young-Wilkins plus a shorter walk in the area.
You'll like the Young & Wilkin valleys.
If you want some other things to do, try Mt Shrimpton up behind Makarora village, or get the Newmans Coach further up the highway to Fantail Falls south of Haast.
You could take a jaunt up to Brewster Hut and spend a couple of days poking around there.