That stinks. At least you realize how much it bothers you.
I've been married longer than you. Have never had dual significant events on the same day. Double whammy. But multiple times events have only been acknowledged with words in the morning and a card made via printing out an online card! What as helped me is that I no longer jump through hoops buying presents, etc. Though I still cook. For a long time I was bothered because I felt like I did so much more. No longer. I don't worry about it anymore.
And my husband just simple adores his mother. Yours is probably the same way. It is helpful for me that lately, I've learned to love her more as well. But I know the mother in law thing is not always easy.