Alcohol personal licence

I work in a alcohol experience and they allowed to get in people under 18 years. We have people from all over the world and of course if they do not show the id we just target then as non alcoholic. sometimes parents give a sip of their drinks to their 17 or 16 years kids.

As a alcohol licence holder I am allowed to tell those parents to don’t do that?? Of course we always very strict to policies to don’t serve to under 18 but how to deal with the parents.

Thanks