My mother sends me religious emails all the time. She prays in those emails. Those are more frequent than some piddly card.
I don’t subscribe to mainstream religion. I don’t like being prayed over, unless the person genuinely cares about me.
Do I fuss and complain, and expect my mom to adhere to my belief system? Fuck no. She’s my elder, I respect her [but I do not love her, that’s another matter]. Old dogs can’t learn new tricks. I just skim the emails for substance, and delete them.
There’s no point trying to make it a two way street with your elders. Just take what is handed to you, filter it, and toss it aside. Doing otherwise will just cause unnecessary rifts.