As American citizens, do we need two visas? A reentry visa for AU? How does this work? I've received conflicting information.
As an American citizen you need an Electronic Travel Authority to enter Australia. This serves in lieu of a visa and allows you to visit as many times as you wish for one year after issuance, for up to three months per visit.
You do not need a visa or advance authorization to visit New Zealand under its Visa Waiver program.