OK, so here's the question: If your ex wanted to do something nice for you for Mother's day, what would you think of it? How far would be good to acknowledge that he NOW realizes that you're a good mother, and how far would be too far? What would creep you out? How long have you been divorced and what would you have thought if, the first Mother's day after the separation, he had said he wanted to take you and the kids out to dinner togehter?
I've always suggested that people do the shopping with the kids for the other parent, for birthdays and parent's days, but other than that, anything else is unnecessary and maybe unwelcome.
So... also, what have been the things that he has done with/for you for mother's day since the separation that have been good? And if he's done nothing, was it good? is there anything he could have done that would have made you happy?
And if you believe that being together would have made you happy, is this because YOU had been hoping for a reconciliation? And if you did NOT want reconciliation and he wanted to be together with you on Mother's day, would you have apprecitated it or been put out by it?