Hello Chip;  I don't think what dropped on your sons head was
coolant/refrigerant.  What it likely was is water condensed out of the
humid air.  I had a similar situation happen to me in a 73 van I had with
AC.  It was a hot humid day, me and my 2 older sons were going to go down
to the swimming hole for a dip, the last 40 to 50 feet were a quite steep
drop.  I stopped at the steepest part of it to look for a spot to park.  It
felt like someone had emptied a bucket of ice water down my neck.  I
suspected the mischievious one (Jeff) was getting even for some little
transgression, but he was sitting in the back seat, too far away to have
done that.  Turns out the drain hose had pulled off the pipe, and the water
had been pooling in the AC housing until it was tipped downwards enough to
release it.  I opened up the plastic and put the hose back on, but it fell
off once more before I sold it.              Larry Carter