I show them that I've gone out of my way to detail it all on the Internet so they know how to circumvent it ;-).
That said, decoy wallets are a cheap way to address this sort of thing, though there's always the question of if you have more. A time locked multisig might suffice, as you could show them the script itself and the fact that your coins are locked up for another 6 months (can I make you a cup of tea while you wait?). If you've got a metric fuckton it may be worth considering insurance from Anchorwatch -- just give them your coins, let the insurance pay out, and let Anchorwatch hunt them down like dogs with backing from Lloyds of London.
