I think you're going into over-explanation mode again, though. It's not really that difficult for them to understand why they can't be of much help; it's just a case of "people are complicated" and "strangers intervening in family affairs tends to cause more problems than it solves." (Or is that a cultural thing?)
(I don't think Harriet's parents are going to be too worried about a DVD when there's bigger fish to fry.)
