I'm concerned your children. Being introduced to the OM as though he is just a friend. He played a big part in the destruction of THEIR family. OM is not their friend and is not to be trusted.
I agree with GB 100%. Telling the children that OM is "just a friend" is perpetuating a lie that your WW started a long time ago.
However, I don't think it is your job to clarify things with your kids. It is not healthy to talk about your WW or her behavior to your children. They need a mother and they need to see her in the most positive light, even if you know otherwise. They will find out on their own when they are old enough to figure it out. It is in the same spirit of letting your WW make her own mistakes. It is her lie to tell, and she has chosen to tell it. I think it is sickening that a WW can lie to their children as effortlessly as they lie to the LBS. But, it is beyond our control.
I was thinking about putting a "boyfriend clause" in the divorce - stating that any new beau in a parents life must be kept from the children for 6 months. This would apply to me equally. It would be in place to protect the kids. Have you thought about this?
Rip, I feel your pain because I am going through it too. I am surprised how mild-mannered you seem about it. Amazing how you can tell her that she is a great mother. I could never bring myself to say this. I think my resentment-meter is stuck on high. Kudos to you.