Wow. I mean, just wow. This was an incredible experience, and one of the things that makes New Zealand unique. You can see kiwis and other endangered wildlife in zoos or other smaller places, like kiwi birdlife park in Queenstown. You can also get out and do a true wildnerness experience, like bird-watching on Stewart Island. Zealandia is somewhere in between those types of experiences, which makes it ideal for families with younger children. My wife and I would have loved to spend a couple of days camping on Stewart Island. Our kids? Not so much. The virtue of Zealandia is that it's real. It's not a zoo, but a working wildlife sanctuary that is intended to create a predator-free environment that restores, as much as possible, the conditions of pre-human-contact New Zealand so that flightless birds and other wildlife can flourish. It's integrated to some extent with the surrounding environment. Birds like kaka, tui and bellbirds come and go. Keeping predators out is a constant challenge for this reason, but they seem to be doing a good job with the fence.
I highly recommend taking a guided walk with a ranger. Our guide not only gave us a lot of information but showed us where to look. There are feeding stations set up where you're likely to encounter wildlife, but it helps to know where to look to see things like tuataras and wetas. My daughter spotted a tuatara, but wouldn't have seen it if our guide hadn't pointed out a spot where they like to hang out. A highlight of the visit was seeing the incredibly rare takahe, of which there are only about 250 remaining (if memory serves). Seeing kiwis requires going on a tour at night, which we didn't do, but as there are numerous kiwi within the sanctuary it would seem like pretty good odds of seeing one.
The park is an easy walk from the cable car stop in the Botanic Gardens, although there is a free shuttle that departs from the i-site downtown.
We ate lunch at the cafe after the visit and thought the food was decent and reasonably priced. If that doesn't suit, there are many more options within walking distance in the Kelburn neighborhood.