You are the reason for his smile and every happy moment he lives. Your dad has been deeply concerned for you at every walk of life. Its the special day of his life. Why not make an effort to make his day a little memorable, by sending him the feelings of your heart penned beautifully as a greeting card. Sure he is gonna love your gesture and way of expressing your love for him.

Your deep care and concern about my well being
makes you the best dad in the world
Thanks for always being there