I understand what you are going through. I am not saying this is right or wrong, but I choose not to have any contact with him regarding the kids activities or inlaws. This prevents those "feelings" from popping up. You have to live like he is not in your life at all. My ex looks at these little "connections" as control and control equals being his mother. If my kids have activities, they will tell him or he can look it up on the school website.
Me: 46 H:44 Together: 25 years Married: 20 years Separated: 11-30-06 Divorced 12-21-07 OW: EA began 2005 PA began end of 2006 3 children,20, 16, 6 ex asked for forgiveness 01/16/11