As far our your kids moral compass - that is a tricky one when you have one parent modelling a complete lack of morals.
I would hazard a guess that they know where you stand on these matters so talking to them about it would be like beating a dead horse.
IMO all you can do is live in a way that is true to you and true to your morals. You have no say nor control over how he lives or what behaviour he models.
You continue to show them how healthy people live. In time he will blow his life up enough that they will see.
Don't mistake them accepting him for them agreeing with his choices. A lot of these kids have to bear the burden of their parents choices in order to maintain a relationship with them.
Don't let this become a wedge between you and your children. You keep doing you and let him keep doing whatever the hell he calls this life he is living.