Where in hell did anybody tell you to drop off your girls and go hit the clubs?
You would not be in this position if you had set a boundary the MOMENT your W contacted you about this dinner.
I am sorry W but having a b-day dinner with your father on my night with the children is not an acceptable plan to me. Your father's blatant disrespect towards me does not result in me going out of my way to accommodate HIM or YOU on MY night with the children. Me and the kids will be at <insert restaurant here> tonight. If you care to join us to wish D8 a happy b-day please let me know by <insert date here>. PERDIOD.
Her options then become limited - respect your decision and time or not. If not then she doesn't get to eat a b-day dinner with her kid and that is a sad little consequence of divorce.
Now all of a sudden you are worried about confusing your kids?
