I like the various thoughts, and I'm definitely filing some away for future use, but I think I'm going to go with the following:
Last year, a UK member of the White Council went off the deep end out of despair (possibly helped along by a discreet WCV) and began commiting familicide (descendant-cide?) after the death of one of his beloved great-grandchildren. Not wanting to have to face that pain again, he came to the deranged conclusion that it was best to just make a clean sweep of it, all at once, and save himself the future pain. He got through about 3/4 of his extended family before he found out that the derided coppers of his own youth have left their own highly capable successors who have definite thoughts on little things like hostage situations, serial killers and possible domestic terrorism. And, as he only
believed (and was thus magically capable) in killing his own descendants, the police shot first in a tense situation. Wizard dies, the Wardens are a little late to the party, but they're occupied with the Red War and they at least engage in a little clean-up and coverup.
Now, one of his great-great-grandsons, living across the Atlantic in the US, has an accident; a fatal one. And his 13-y.o. son and two preteen daughters managed to survive in the back of the car, but he and his wife were killed when they swerved out of the westbound lane and into the front fender of a Mack truck in the eastbound at a combined speed of about 150 mph. The survival of the kids is being called a miracle (of car safety design). The kids do have some latent talent--all of them--that comes through their mother's side, but they had a bit of help. Their maternal great-grandmother, also a magic user (but not a full wizard, sadly) made a bargain with a
Black Shuck (a semi-benevolent black dog spirit of the UK) to watch over her line.
As a result, witnesses to the scene will report--erroneously--that the car swerved to avoid hitting a large black dog on the freeway; this should hopefully make the spirit's job alot harder and the ghost's easier. (And given some of what else I have planned for the main plot--that should be more than enough possible complications to keep PCs occupied)