(1) when we were married, mother's day was, according to my ex, a bogus commercial holiday designed to sell crap cards and flowers that didn't deserve any celebration, (father's day, was, of course, something to celebrate), and
(2) since we've been divorced, my ex has made not even the slightest token of a effort for any holiday (mother's day, my birthday, Xmas) in regard to me, and
(3) all the help DD's wanted/needed getting stuff for me or making cards for me, etc. (for any holiday) has come from my mother,
I will suggest and encourage (gently) that DD make him a card, help her make one if she asks for my help, and have her call him on father's day and his birthday.
Beyond that, nada. Zip. Not from me.
His girlfriend is welcome to take DD out to buy my ex something for his birthday, Xmas, father's day, whatever, when she's with them (in anticipation, late, whatever).