Heck just keep them and watch the value appreciate, we're near parity. A big rise from when the Pacific peso was only worth 50c US.

A more pragmatic solution, do your airlines have change bags/envelopes for charity which accept foreign coins?

When flying QF (domestic at that!) they have an envelope in the head phone plastic bag which actively seeks foreign coins. The charity concerned has a deal with the bank who gives them appropriate value for all coins.