"I would stop them from driving no matter what" is a fairy tale and only children believe in fairy tales. Adults believe in "I would do what I could but there's a point where discretion is the better path -- for everyone involved." There are police officers and first responders who are trained in how to handle such situations and there's nothing wrong with using them. I don't have such an inflated opinion of myself that I believe that the fate of the world rests on me and me alone.
I most certainly wouldn't physically challenge someone I didn't know, anyone I did know that I knew owned a gun or I knew I couldn't take down. Challenging someone you know you can't take down is grandstanding. Challenging someone you don't know or you know has a gun (or other weapon) is stupid. Calling the cops when it's a situation you know you can't handle is smart. And it's not even close to "not even trying." IMO calling the cops actually takes way more courage than trying to take someone's keys away because in our culture we have it ingrained from a young age that you don't 'snitch.' I suspect you risk losing friendships over taking that path, in fact.