I'd be so happy to help. My ex has been shacking up with his girlfriend for 19 years... 7 of those years he was still married to me. If they got married, it would certainly help my attitude about my grandkids calling her "Grandma."
This is just the beginning. "The other woman" will be thrust into your life every time your kids plan any family activities. I've never wanted my kids to suffer for their parents actions. I told them that if they wanted me to sit in "her" lap at their wedding, I'd do it with a smile... my tongue would probably be bloody from biting it, but it's not about me, it's about my kids.