Re: I could use some advice...
I would ask her if there was a reason she didn't acknowledge your children's birthdays. She needs to know if she's hurting your feelings, because its causing you to be upset. I would if its because she doesn't want to exchange gifts, etc. Also let her know that your children notice that she doesn't call on their birthday. There may be a logical explanation. Does she acknowledge the birthdays of other children in the family?