I've got to agree. 4.5 hours really isn't very long. There are a couple of places to visit relatively near to the airport, including Butterfly Creek, but it's very overpriced for what it is, and the butterfly house is really hot and humid, which isn't something I'd recommend doing straight after a long flight. The airport is not in the nicest part of the city and quite some distance away from most of Aucklands places of interest. The shuttle bus/taxi ride to the CBD alone can take 30-40 minutes or more. By the time you've done that both ways, that doesn't leave an awful lot of time to do anything without rushing, especially once you add it the time it'll take to get through MAF and customs. Personally, I would recommend grabbing a coffee and going upstairs to the viewing gallery. My kids enjoy watching the planes taking off and landing, and there is plenty of space for them to run around a bit.