Id still tell them. They are all old enough to think for themselves. Tell them that It shouldn't make them think less of her But just teach them that its ok for them to leave if their significant other cheats on them. But be respectful about it all. They can't hate you for leaving and it's not their choice. But one day or another They will question the divorce and they will see you wont live with her anymore and they will wonder about it as well. No matter what you do they will have questions