Your profile states you’re located in NSW.
I suggest that you attain a
“Working with Children Check” reference number from the NSW Government’s Office of the Children’s Guardian.
I understand that document is recognized interstate, throughout AUS. I have found it a very useful document overseas, too.
That’s what I would give to the Security Guards, not necessarily a business card.
It was your choice to pack up your gear and move on, based solely upon the Security Guard's report
"3 parents had complained about me taking pictures": prima facie that probably wouldn’t have been my choice.
https://d6d2h4gfvy8t8.cloudfront.net/18420327-orig.jpg
Little Girl and her Dog - Venice 2012
Mum and Dad were inside the house when this was made. I called them out to show them the photo; made a few more of the whole family. Sent them a few of the files and got a nice 'thank you' note.
***
Notwithstanding my absolute agreement with the opinions contained within Rick’s commentary, specifically and definitively
the need for street photographers to be good communicators:
it is also my opinion that
a default buckling under to irrational societal pressure, is definitely not the best course of action and doing so will lead to a poorer society.
WW