I'm young enough that I have very rarely had to deal with these sorts of emails first-hand.
I think older folks just haven't been trained in the right data set to recognize these things, so they are more prone to indulging them than the average person. Reasoning with them on the level of individual errors probably won't produce results because their entire paradigm is wrong.
You might consider sending an article on how scammers work; e.g. they intentionally introduce spelling errors to text to filter out those people less likely to be duped. A lot of the characteristics are shared with these sorts of emails.