Not a Boffin,
The CAA have a well laid down set of criteria for what constitutes a 'display' and it has nothing whatsoever to do with the number of people that may be watching at the time Sir. The same applies to a scheduled 'test flight' also, so the info you have been given is not correct.
I am with the cyclic-fondler and forget on this issue. It would be a massive
PR gaff if they did not announce the date of the first 'flight' albeit only a test flight. The publicity would be enormous and would rejuvinate many of those supporters who have perhaps lost a bit of faith and interest in the project.
That said, there is clearly a danger with having loads of GA aircraft 'poodling around' but that should be controlable with the necessary NOTAMS etc.
Either way, lets not hide this event away, it needs to be brought to the fore to show the supporters and the public alike that things are progressing with the old girl.
The Winco