Australia, New Zealand & the South Pacific - Queenstown to Christchurch Help

We will be driving from Christchurch to Queenstown on November 15 to 17 stopping for the night of the 16th at the Westwood Lodge north of Franz Josef Village. We plan to return from Queenstown to Christchurch on November 19 arriving in Christchurch on the 20th. Our dilemma is which route to take and where to stay the night of the 19th. We had planned to stay at the Hermitage at Mt Cook Village but the hotel is sold out. We are not wed to any particular route and would like some help.

I'd drive back through MacKenzie Basin as you planned - the scenery is different to the west coast route you are taking in, and less tiring driving.

IIRC there are other accommodation options at Mount Cook Village (motels, B&Bs), or you could stay at Wanaka or Tekapo along the way (or closer to Christchurch at Geraldine).