With the best will in the world, friends and family will want to see and share life stories, photos and videos of your kids. That’s natural, and it’s not something you need to ban outright.
What you need to do is to ensure they understand what’s acceptable to share online and what isn’t.
In an ideal world, people would always ask you before putting multimedia online that included your kids, but as we all know, that’s not always the case. At least if you preempt those occasions by telling them what’s acceptable, and what’s not, they will hopefully be more thoughtful.
It’s hard to dictate to other parents when photos and videos include more than one family. At the very least, you could ask that they don’t tag the child directly (if your child is young then they probably don’t have their own accounts anyway) or tag you, the parent(s), instead.
You’ll probably already have explained to people why you can’t share specific information about your child’s history. Hopefully, friends and family will respect your wishes if they understand there’s a genuine child protection issue at stake here.
When all’s said and done, photos and videos will slip through the net (no pun intended) from time to time. Even then, the risk of identification by someone else are slim, so do the best you can with this one and then don’t stress about it.