Let it go. When you divorce your ex can do whatever he wants to celebrate with his new partner and involve your kids since its his time with them. This is the type of crap that will hurt your ex’s relationship with his new partner and drive a wedge between your kids and her. Which is probably what you want, sadly. My daughter has spent almost every mothers day with her father/girl friend and then step mother for many years because thats how the custody arrangement worked out. Find something else to do and stop trying to create drama. You talk of being a role model but your behavior is anything but mature. Celebrate Mother’s Day with your kids on another day.