Offtopic: how about Grails Grannies?
It is always said that crossword puzzles and sudokus are great for the elderly people as those simulate their brain. And stimulating/challenging their brain helps to keep the brain healthy which will give them better opportunity to be thinking straight till the end.
Sure, not all grannies could or even would like to code but the same applies with Rails Girls: they do have a certain demographic that is interested. And because so many other girls are going, it decreases the threshold to participate (coding usually sounds really scary!).
My grandma didn't want a computer or Internet at first. But she got one as a present and now she is a Facebook addict. I really don't see why she also couldn't start coding if she would be getting good and easy instructions. And that would keep her busy ;)
(hmm.. maybe I just have this weird fantasy of having a hacker grandma which I invented as a child, not knowing what hacking meant... That just would have been so cool :P ).