International Antarctic Centre
If you are in any way interested in what goes on down below in Antarctica, you will love this place. Kids can play in the snow room or you can go on a Hagglund vehicle, see the penguins and generally play with or read a tonne of cool stuff. The interactive museum is near the airport so you could theorhetically visit on your way to a flight, but do make sure you leave a few hours as there is a lot more here than most people imagine. There is a free bus which runs from Cathedral Square.
read more about International Antarctic Centre