It is not about your and her it is about your children. She is still their mum and they will want to give her something. Do it for them.
Dont make it too personal - i got my H a card from each of the girls and a small silver key ring with each of the girls initials on fathers day. He does the same for me. This year I got cards, flowers and a bracelet. It was his day to have them but he didnt hesitate when I asked if i could take them to lunch even though he had planned to take them around his mums form mothers day lunch. He took them in the evening instead. The girls asked if i could join them and he said sure as Kong as mummy is ok with it. Children shouldn't be used as pawns. I may not like everything he has done, but i respect him as a father. Your W will respect you as well, but more importantly, your children will.
