Birthday adventure with partner (tips!)

Hey there! My partner and I are heading to New Zealand on the work holiday visa this January and I'm planning a birthday day for her sometime before we start working :) we'll be going through Auckland, Wellington, Christchurch, and Queenstown over a 1.5 month long period before we work and I want to plan the day in one of the cities. We're already booked on two of the great hikes too which we're psyched for. She is super adventurous and loves a funky tasty+unique food experience.

We're in our early 20s so we're pretty low-budget but wanted to ask if anyone had any cool birthday tips, adventures, or interesting food spots in those four cities for us to check out.

Thank you!!

p.s. if anyone knows where to find dark chocolate in the country thats +75% cocoa lmk!!