Birthdays carry meaning for the Christian family across the long arc, even where no liturgical observance marks them. The card from a godparent in the early years, the small marking at the family table through the school years, the milestone gathering at 50 or 80, the quiet observance in the last years of a long life: each carries the household's practice of giving thanks for years given. The observance is normally light; the meaning is the year itself.
What the recipient values is the source for how the birthday is kept. For Orthodox recipients, the name day normally carries the weight a birthday card carries elsewhere. For Catholic recipients with a particular patron saint devotion, the feast day alongside the birthday is often welcome. For Mainline Protestant and Evangelical recipients, the warm-traditional card with a brief verse or blessing normally lands well. For recipients who do not particularly observe religious framing on birthdays, the plain warm card lands on its own. The household keeps what the household keeps.