An example of how the trip can run:
Day 1: Meet your guide in Wanaka or Queenstown, check gear and drive to the Fantail Falls carpark on the Haast Pass Highway (1hr). Cross the Haast River and ascend through the silver beech forest and open tussock tops to Brewster Hut (3-4hrs)
Day 2: Hike above Brewster Hut, sidle around onto the Brewster Glacier and climb either the West or South Ridges to the summit, return to Brewster Hut.
Day 3: Contingency day or if your legs are up to it, enjoy a simple climb up to the top of Mt Armstrong.
Day 4: Walk back down to the Fantail Falls carpark and drive back to Wanaka, stopping along the way for ice cream in the small rural settlement of Makarora.