Joyeux anniversaire ! Que cette journée soit remplie de bonheur, de rires et de merveilleux souvenirs. Profite bien de chaque instant !

My Father,

Allow me to wish you a very happy birthday. I hope that God protects you and continues to assist you in all the good deeds you carry out for the parish.

I believe many people love and appreciate you.

See you very soon,

You can keep it even simpler. Otherwise, there are other texts, some of which are well-suited to your needs as they are very basic: https://www.merci-facteur.com/modele-texte-anniversaire.php

(Avoid copying and printing a model text. It would be better to write it by hand)

As for the design of the card, you can choose either a simple blank card with no image, which is what I would choose, or a card with a very simple nature photo.