Sain wedi'i Rhannu

AITAH for attending a birthday party thrown by my former ILs after my ex-husband's wife suffered her third miscarriage? My marriage ended because of my ex-husband's cheating with his current wife. We had a 4 year old, 3 year old and 6 month old together at that time. He didn't want to work on things anymore than I did by then. Our divorce was not amicable but I have worked on being civil for my children's sake. My ex-husband's family and I have remained on good terms and I'm actually godmother t