Why don't you use a 3rd party age verification service like the site APD Nudes does. They also have a second method as well as the 3rd party age verification service which is submitting id to them via their support desk. Look at the APD nudes link below and it tells you about their age verification methods
https://apdnudes.uservoice.com/knowledg ... rification
https://apdnudes.uservoice.com/knowledg ... rification