Personally, I have not known any parents who were contacted by the security services. On the other hand, those services have contacted the young people directly, and that causes panic on the part of the young people and fear on the part of their parents.
I have even seen the case of a child who was 18 years and one week old. CSIS went to his home to see him, instead of contacting his parents, which would have been much better. Because he was 18 years and one week old, CSIS had certainly had the matter in its hands for some time already, and actually waited until he was 18 to take action.
I strongly advise against that kind of approach, given that a parent will want to protect their child.