Thank you for reaching out to us.

In Temple times, when mikveh was relevant for handling ritually pure items or entering the Temple Mount and not just for the marital relationship, mikveh use was more likely to be public knowledge.

In some Sephardi communities, it has remained something that women are more open about.

At the same time, a couple ordinarily is presumed to have relations on mikveh night, which is a private matter that couples typically do not wish to divulge to others. Indeed, Rema (Yoreh Deah 198:48) rules that it is customary for women to keep mikveh immersion private. 

If you have reason or need to share your immersion with your son, then you may. But ordinarily, it is considered more proper not to share, even if this involves a misdirection. If there is a specific challenge that you have been facing with this and would like to discuss, we'd be happy to try to brainstorm with you.

Please let us know if we can be of further assistance.