Is this the same couple whose daughter you have trouble with at the lake? They sound familiar from your descriptions of them.
If so, you've somehow managed to live with this type of behavior for quite a while.
Since he's been discovered, and his wife knows too, I don't think there's much you can do to let be known what a "snake" he is. It's pretty clear to all involved.
So, I concur with others who say to let the wife handle it. However, reading between the lines (and I may be wrong) it seems OP isn't content or doesn't think justice will be done by her friend to her husband to the extent that OP desires. This is why I asked my original question. If this is the same couple, you've lived with them (his ego/her ambivalence) in the past.
If it's a different couple, why do your friends pick dipsticks for husbands?