The grass runways were deemed unserviceable by Avalon airport staff and the WW1 guys decided that they wouldn't fly at all if they couldn't launch everything.
There was a NOTAM issued for AVE but it was a bit delayed getting out as the airstrip had to be inspected after first light then the safety officer had to get back to main and his office to issue the NOTAM. I imagine it was a YMMM NOTAM.
Some GA was squeezed into main but arrivals has to be stopped prior to the air display commencing.