Some thoughts

Do you like star gazing type activites. St John observatory near tekapo runs programs at night at their observatory. It's a couple of hours .moves was midnight to 2 am and you could if so inclined drive to twizel after that for the night.

dundelin is great..one of our favorite places and the otago peninsula is beautiful ..there is an albatross colony at the head of the peninsula and elms wildlife tours runs penguins and seal tours that start mid afternoon on some private land on the peninsula as well as short cruises around the peninsula. . There is a wonderful botanic garden there as well. We've stayed at bluestone on george which was apt like hotel distinction which was a former post office. There are also some small but interesting museums and architecture there. the short lighthouse hike at nugget point south of dunedin is also mice but don't think you have time.

Wellington..don't miss te papa the national museum and you could have a nice dinner at hippopotamus restaurant in the art museum hotel across the street

We've been to NZ multiple times and are headed back next week and imo queenstown is one of the least interesting places. Way too touristy crowded and expensive. We drove last time from christchurch to te anu ..which was iirc about 10 hours with stops and enjoyed the nice small town atmosphere of te anu compared to queenstown. The lake is really nice and it shaves hours off of any trip to Milford or doubtful. We did a half day Mitford trek from there which was also nice.

With so little time in each place don't have your heayiyset on heli hiking or glacier that are very weather dependent.

Mt Cook also adds a lot of time driving. It's one road in one road out so just depends on how you want to spend your time.

There is always more to see and do than you can plan for. Better 2 or 3 great adventures vs racing to try to do too much. Stop and soak in the views and you will be well rewarded..it keeps us coming back again and again.

My two cents