SI, your parents are at least in their 40s, right? All those nasty little ailments of old age will be showing up soon. Mom's touch of arthritis shows up, or Dad gets a little skin growth removed- pounce on the chance!
Educate them! They have been fed the governmental "Pot is a dangerous drug" line- forgive them that- they were brainwashed as kids and believed it! Just keep Granny's list (link below) in the back of your mind for that day!
Granny