I know I've offered already, but could I make sure I know what you're talking about - previously when someone's asked me to "sort em out" it hasn't involved spark leads! (Well ok, maybe once, but she was weird!)... I don't want to get a *shock* when I get there!
On a serious note, you may want to discuss insurance (and worst case scenarios) with whoever the lucky volunteer is - it'd be gutting for both parties if something happened during the trip to the valet place. It may even be worth asking your insurance to add them to your policy fully comp for the day - the insurance company may do it for free considering the circumstances.