Wow, sounds like it was a hell of a bang.
Even though it wasn't a "direct hit", lightning is basically a huge static discharge. That can wreak havoc with electronics.
Just to give you an example, every winter I've got to be really careful if I walk across the room and touch my laptop. The central heating makes the air so dry, I give off a static spark whenever I touch stuff. I've got to be really careful to touch a metal connector on the side of the laptop to discharge myself first, otherwise I'll completely lock-up my computer. Even the power button won't work then. The only way to reset my laptop is to unplug the power supply, pull out the battery, and let it sit for about 5 minutes. Then I can boot it up like nothing happened.
Back to your parents' vehicles. After you've made sure the fuses are good, I'd try to do a "hard reset" on the vehicles' computers by disconnecting the battery for about 30 minutes. Try touching the positive and negative battery leads together (with the battery disconnected, of course!
), to drain off any residual voltage.
I don't know if that'll work, but it's worth a try since it costs nothing, and you won't be any worse off if it doesn't. Failing that, my guess is that one or more computer modules were damaged, and I don't even want to think about what that would cost.