[averyrm]

Seems that this, like many aspects of aviation, is a fear that will subside with experience and knowledge. JRH had some good ideas. To add, point out when you're flying below/near jets how you know you're safe where you are, visual cues and etc. Get the AIM out and show how controllers need to keep you safely away from wake turbulence, and what you can do to negate risks associated with it.

That said, make sure he doesn't get complacent on TO/Ldg behind heavies, it's more dangerous than a lot of people seem to think.