Mrs. W.,
When I posted a comment yesterday, I had only gotten to approx. page 3 of your thread. Now, having reached page 12, around which a discussion begins about your children and whether you thought of them during your A, I realize I have some questions. First, however, I want to explain my backstory (and please forgive me for my text length) but you have been thoughtful in your responses to others thus far and I hope maybe you can help me to see things from the other side, after all these years.
You see, I am not just a BW, but a BC (betrayed child, for those unfamiliar). My bio mother had a PA on my bio father when I was 10. I think the A lasted a couple of months; maybe no more than 3. My father is the one that told me about it. He took me for a car ride around our town and basically vented. That messed me up for a few reasons.
1) I don't believe that he should ever have used his 10-year-old child as a confidante. I don't remember every word, but that conversation was a mix of him, telling me the details of his discovery, and also expressing his feelings of anger, disgust, resentment, etc.
2) It shattered my view of my mother. By this time, I was VERY close with my mom. I prided myself on how the adults in my life would tell me how much like her I was. She was/is beautiful, extroverted, a social butterfly. When I discovered that she had an A on my dad, all those good things shattered to pieces. Who was I if she wasn't the person I thought she was and I am meant to be just like her?
3) I guess I realize it broke my trust of her in general. She and my dad used to make a date night of going out to a dance club. She has always been more outgoing and loves being the center of attention. She was always begging for my dad's attention but as their marriage continued, he withheld affection and became very ornery. He has a ton of his own FOO issues. (As a grown woman now, I can see how this set my mom up to feel desperate for any kind of love.)
So, after awhile, my dad told my mom to just go out dancing with her girlfriends alone. She didn't want to (I remember her telling me how much she wished he would want to go with her) but she did as he suggested and it became a weekly thing. I would help her to pick out what to wear and help her fix her hair and makeup. When I found out about her A, I felt like she had used me to get ready for some OM. Her own daughter; asking me if she looked nice after we worked on putting her together, was helping her to look nice to parade around in front of a man who wasn't my father. I felt disgusting by proxy. 
Anyway, I remember very clearly how extremely PISSED my mom was to discover that my dad had told me everything. She told me "it's none of your business". I was so hurt because that seemed like such a cold response. Now that I am a woman, I think she was just embarrassed and mortified to have her kid know the bad thing she had done and probably also was angry because she thought she could protect me from it but my dad had already beat her to the punch.
It took MANY YEARS for me to regain a closeness to her in my heart (which she doesn't know about to this very day). It took many years for me not to cringe whenever someone would compare us and tell me how much like her I was.
Unfortunately for my parents, I believe the A was a deal breaker. It ruined their marriage as they knew it. Unbeknownst to me, my mom tried to suggest a divorce, but my father threatened my mom about having ways to keep my brother and me from her forever. She stayed because she was scared to lose us. She believed him. Then, he told her that he would "make her pay' for what she did. And I believe that these last 24 years have been nothing but him doing just that.
I directly contribute my anxiety disorder to my upbringing in a house full of tension/hate/anger/bitterness because of infidelity. There was always a lot of yelling between them, and name calling. And when I got older, somewhere around puberty, because I truly am so much like my mother, and now was looking as much the woman as she is, my dad directed those feelings at me. He always threw in my face, "You're just like your mother," as much as if he were cursing me.
I vowed that I would never be with a man like my dad, actually. When I found my xWH, my biggest concern was that I didn't think he was anything like my father. I never thought to wonder if he were anything like my mother. And then BAM! He cheats on me and I have to relive the pain all over again but from my father's perspective.
It brought up all the old feelings I had with my mom and a few months out from my Dday, I argued with her a lot. She goes to therapy and she even mentioned it to her therapist. We had a joint therapy session together, and unbelievably, her therapist told me that my husband cheating on me and my mother cheating in my childhood should not merge together but how not? 
I read a book with a title, something like When Parents Cheat. It was helpful. It even explains how we tend to find life partners who we subconsciously choose to help us live over childhood traumas, as a means to finally resolve the issues. Every year since that therapy session, I have considered buying a copy for my mom's therapist as a Christmas gift.
Anyway, if you have read through all of this up to here, I really do appreciate it. I shared it so that you would understand the context of my concern for your kids.
First, I know one of your daughters is married and I am assuming the other daughter is also older, at least, than I was during my mom's A. When it comes to your two boys, I am assuming you haven't told them about your A because of their ages.....but I wonder why you and Mr. W. are planning to tell them at all. I am not certain that my knowing really helped me. I guess it explained why there was so much hate and anger in my house, but other than that it wasn't good for much. It really damaged my relationship with my mom for a good long time.
Besides, I hope that if the moment ever comes when you realize that home life is becoming like a war zone, you and Mr. W. would try not to force it. Some people say they stick together "for the kids" but it just does more harm than good. I have only ever wanted to see my parents happy rather than living in this Post-Infidelity Purgatory. You seem, through your writing, to be very intelligent so I know you know this but I included the warning for others who may be of the "for the kids" mindset.
It would have been nice to have seen my parents in a healthy relationship...and perhaps I wouldn't have chosen a mate who would cheat on me? Maybe that's not fair. My mom thinks I blame she and my dad too much...but kids are a product of nature/nurture so what else?
So, in case it was hard to find my questions:
-Why are you planning to tell your sons?
-Where did thoughts of your children go when you were actively in the A?
-What do you think your children are learning from their therapy sessions and/or what have they told you directly about them? (BTW, I am so glad to learn that you got them into therapy).
-Do you or Mr. W. ever rely on your daughters as a shoulder to cry on?
-If your AP has children and they wanted to contact you, would you be ok with that?
Thank you so much for your time, if you survived the wall of text. Honestly, this was therapeutic for me to write out but it's also rare to be able to ask a female Wayward these questions and know she will respond sincerely. I really think you respond sincerely. My mom, to this day, is very uncomfortable with discussing her actions. She plays the victim a lot. So thanks.
