Checking IDs - legalities and ethics

Hello Perth Tessitura Community,

Could somebody please help me to understand the legalities with checking and storing IDs?

West Australian Opera is organising a series of events for audiences 18 to 30 so I need to know if ticket buyers fit in the age bracket.

It seems that the most efficient way is to ask on the event series webpage to upload a photo of the ID card (this would also act as a deterrent for people not in the age bracket), then to store the ID card somewhere safe, meaning that they only need to provide the ID card once if they attend multiple events. 

Is it safe and legal to store IDs on Tessitura or our server? Are there any legal implication or rules I am not aware of?

If so, do you have other ideas/examples on how this could be done?

Thank you so much,
Rebecca