My stepmother was all about the immediate act right in front of her (all other Mother's Days, past or future need not apply), not specifically the content, but I did not realize that I don't think until I was grown. I had a great gift I wanted to give my parents one Christmas but it fell through, turned out not to be appropriate and I was in college with limited time to shop and no Plan B so did not have anything for them that year and you'd think I'd stuck a knife directly into her heart.

Generic/"average" cards with culturally "expected" sentiments could work fine. All mother's day cards are going to talk about love, and care and "mother" sorts of topics and if you ignore that it is not at all how you perceive your own mother or how much like that she actually is. . . "it's the thought that counts"

Protecting one's own heart is a good idea; just do what is "expected", smile, and pretend a lot and try not what you want on that particular day. This mother's day I am hosting a party with my stepsons and their mother, my husband's ex-wife. She thinks we are best friends.