Do not cover for his lies ever. Do not cushion him from any consequences of his actions. Ever. Doing so says to D11 , D9 that it is ok to keep secrets. That it is ok to Break vows and betray. That it is ok to be treated this way by a man.

D11 and D9 already know something is up. This will really mess them up meeting up with Daddies friend with kids.

They are going to be more hurt in the long run with you keeping this from them.

Families are build around truth , responsibilities ,openness and trust.

Not only will they be grieving the loss of the marriage.

But they will also be grieving the loss of a person they thought was perfect.

You can attempt to shield them from this but it will unravel. They can either find out from you who loves them. Or when they watch that horrible woman interact with their father.

I think you do not need to question OW's character.

She is a poor excuse of a human being. Who would do that to her family and yours.

Flowers always make people better, happier, and more helpful; they are sunshine, food and medicine for the soul.
unconditional love is awesome!