The main thing i did with my parents (don't have grandparents anymore) is that they can call me anytime something unusual happens. One of the thing that you did not mention and at least here happens a lot is someone going to people, mainly old folks, telling them that their son/daughter "John/Mary" (getting their kids names is not hard at all, takes like 30 seconds on facebook or something) asked them for something like to change some bank notes because new ones came out, or their car keys because they need to take it to rotate the tyres, something like that. Crazy stuff, but a lot of people fall for it.
Main thing here: if anything strange happens or you are unsure of something, call me.
Main thing here: if anything strange happens or you are unsure of something, call me.