I've assisted with three driving interventions. All three worked without long-term family problems though one impaired driver did contact the (already informed) local police.
1) Have good alternative transportation arranged. This is essential. Quality is important.
2) Let local law enforcement know what's up.
3) Arrange for car removal.
4) Gather the impaired driver and others at a location away from the car.
5) Explain the alternative transportation arrangements and then mention the car(s) have been removed to a secure location.
6) Contact the former impaired driver daily for a few weeks to make sure all is going well. Help work out any transportation problems.
7) Help the former driver to get a state ID in place of the now-inappropriate license.
8) Assist in the sale or other disposal of car(s).
I may have missed a step above. The process was the brainchild of a long-time police officer who's also a recovering alcoholic.