I hope the rollaboard arrives on time too, but it's a week away so it should. If it doesn't ,use the one you have if it's only slightly larger. You can pack what you need and weigh it on your bathroom scale.
Reading your posts brings back good memories for me. I had dreaded the long flight but the service and food on Qantas was good and there were so many movie options that I dozed and walked and watched movies and the time passed quicker than I'd expected.
I enjoyed all three countries, but especially liked Christchurch, Queenstown and our drive to Milford Sound -- the scenery was so beautiful and so different from Aus. The Arts Center in Christchurch is great for quality souvenir shopping or just admiring good work.
You mentioned South America. I'm taking the Discover South America trip in March but not taking the Peru pre-trip extension. A friend did both and loved both but I'm unsure at this point about Machu Pichu, but things could change.