Hey StJohn...it's no secret so i will explain it to the best of my ability, but i'm not sure of the road names or anything like that.
So i assume that your folks know how to get down to Beacon Ilse Hotel, which is the old skool hotel you can see in the background of this years
Wedge Classic poster
To get to the hotel from the centre of town you have to drive down a moer steep hill and on the way down there's a speed trap on the left hand side. Stick to 40kph and you'll be ok...but you don't want to be going too fast because the turn off to The Wedge is the left just after the speed camera.
Once you're on that road just follow it down into the parking lot and The "famous" Wedge is to your left up against the rocks.
If you don't find the road just drive around and find the hotel, park and walk around to where you can see the fishing boats anchored in the middle of the bay around an exposed reef...and once again...Wedge is in the corner of the beach up against the rocks.
Plett's quite small so you shouldn't get too lost and if you are reeeeeeeaaaaaly lost just ask a local. They should know.
I hope this helps...if not...i will try to explain a bit better.