In fact, it's indicative of skewed priorities on the OP's part that she sees the cheating as worse than the abuse.
Cheating is abuse and her priorities aren't skewed.
Children should be told in an age appropriate way.
18 is old enough to know your dad went with hookers as well. I knew a couple splitting up following the dad cheating and her DD couldn't understand why mum wouldn't forgive. Because that's what we teach our kids and they learn that in schools.
Dad had told DD it was a mistake, mum wouldn't forgive. See how mum was getting blamed.
So DD tells mum she's a hypocrite talking about forgiveness. That dad's sorry and everyone makes mistakes ... we're only human ....that she's breaking the family up etc etc
Well DD soon changed her view when mum told her that while she was st the hodpitsl with dad, as mum was going in for a consultation following a diagnosis of breast cancer, dad was telling (texting) his OW how he was missing her, asked for a pic of her fresh pu**y and said he was hungry for it.
Her mum just told DD he was sexting the OW while they were at the hospital and not the exact words.
She could have left it, but you might excuse her for loosing it and getting blamed for not forgiving . The father daughter relationship is over. The DD has barely spoken to her dad since and this was quite a few years ago now.
The dad damaged that relationship himself. Infidelity affects more than your spouse and has far reaching consequences.
The sooner cheaters realise that the better. They shouldn't blame the betrayed spouse for their crappie behaviour.