I googled 'Uber Auckland Airport' and found this article which states they are not allowed at the airport as of April 2016, unless the driver is registered.
http://www.nzherald.co.nz/business/n...ectid=11623196
Is there a particular reason you want to make sure Uber is available? I would just try the app when you arrive, if it doesn't work take a taxi. They accept credit cards.