Simply put, I rarely see anyone sailing without glasses down here. So if the sunglasses they wear don't get lost/broken, it is likely that once he gets used to sailing with them, he won't lose them, either (unless they don't fit right).

I use a "croakie" style strap and tuck it under my hat. Some tie the croakie (via a small line) to their hat or PFD. Unless the glasses are very heavy, the things will float, and usually be near you after a crash.

I have astigmatism, and have perscription shades. Not wrap around, either.

A water bottle to wash them off helps, and I'm considering RAIN-X, but don't know what it would do to the plastic lenses...

Let him see!