I'm not saying that you can do it effectively and remain free of legal trouble. That's why it's a last ditch option.
Worst case example to prove a point - a mentally unstable person goes wild - there are women and children present. That unstable person can be restrained without serious damage, but that doesn't mean they may not have some scratches or bruising. Again, if you aren't competent in that area, you probably wouldn't have that as an option.
And, once again, that is not a domestic violence situation. The laws are far different if a couple is involved in violence. And usually someone is gonna go to jail if the cops show up. And that often is the man, even if he was just "restraining" her.
I really wish you would drop the restraining advice. That is just gonna get some guy cooling his heels in jail. The best thing is to get the hell out if things start getting violent. And then come back later to deal with the problem. And don't put off dealing with it.