It does not need to get any more complicated than that unless it is a commercial operation for hire and reward.
The proposed operation certainly
appears to be in the nature of "
for hire and reward" as the charity is the beneficiary of a financial consideration in exchange for a flight.
My post was to urge caution - I do not know and am not preempting what view CASA or the Courts may take.
A little more research revealed
CASA Ruling 3/2003 "Application of CAR 206 to operations conducted for the benefit of a charitable entity".
allthecoolnamesarego may be well advised to contact CASA, provide details of the proposed charitable flight and seek confirmation that the flight is within the provisions of CASA Ruling 3/2003? It may be that simple?
Perusal of the aircraft owner's passenger liability insurance or obtaining an indemnity from the passenger may be prudent.
One assumes that those who post in this Forum are professional pilots, familiar with relevant aviation legislation - although I have my doubts, looking at some of the posts in this thread!