My parents don't know what each other want when they die but I do, should I talk to them?

My mom is super scared of planes, first time going on a plane and she emails me what she wants after death, she won't talk to my step dad about it cause it's not nice to talk about

My step dad is scared if surgery so when he had surgery he messaged my partner saying what he wants after death, he won't talk to her about it cause it's not nice to talk about

They both said the other doesn't like to think about it, but they are both going out their way to think about it! They are both religious, so surely that makes it easier to talk about

Both me and my partner know what each other want, like death isn't a taboo, it's the only thing guaranteed in life

What should I do? Im thinking sitting them down and talking to them about it, I don't want it to be an argument, like you went behind my back to do this, but they both did it! So both as bad as each other

But if they die separately, which is most likely, and I say the other wants xyz and they say no I don't wanna do that, I don't want an argument because we don't agree after loosing one of my parents