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 feel it is a disservice not to arm your children with the truth about their lives and allow and trust them to function within the truth as they see fit. They don't need all the juicy details but they should be aware of something like "one of several reasons that your mother and I are divorcing has to do with her inappropriate relationship with [full first and last name of OM]. You do understand that it's not appropriate for married people to date other people, right? Well I learned your mother was dating OM and, even though I was incredibly hurt I remained willing to try to save our marriage. Your mother and OM choose not to end their relationship so because of that and other private things between your mother and I we are where we are. I am not telling you this to motivate you to hate and I certainly don't want you disrespecting your mother or any other adult; however, I tell you this because I think it's important to be honest with you because this is your life too and you deserve the truth about what's going on around you here."
I agree with this wholeheartedly. As the son of a wayward mother, I can tell you that I was and am very disappointed in my father for not telling me the truth. I'm not angry at him, and I don't hate him, but I am disappointed (I do not have a relationship with my mother anymore, because she is still wayward). Your children will be disappointed, too, if you do not tell them. Your WW is lying to them, and by remaining silent, you are complicit in the lie. It is not fair for your children not to know the truth of what's going on.
M 16 T 17 W moved in w/ AP (OW) 5/14 ILYBNIL 5/14 A discovered 6/14 D papers served via USPS 8/14 Filed my response 9/14 D final 5/15...