Simple solution: get the public onside at avalon airshow. You have a stand. Write a flyer stating your case hand them out everywhere and invite the reader to go to the CASA stand and start asking pointed questions in a loud voice.
If the Airshow management objects and does not fulsomely support your actions BY A PUBLIC STATEMENT OF SUPPORT FOR ANGEL FLIGHT, THEN CALL ON AIRSHOW VOLUNTEERS TO WITHDRAW THEIR LABOR. All legal I believe.
I would also approach the RAAF, RFDS and medical services for statements of support.
If Angel Flight gets done over this way, then expect CASA to do it again to GFA, RAA, SAAA and anyone else, including the Avalon airshow itself. Time to draw a line in the sand.
CASA obviously wants to ban private flight and they will achieve it by slowly crushing the sector to death.