From someone who went thru this many years ago. At first I was settled in to the idea of heading to college - a top program. As Spring baseball season started the hype began with all the Pro guys, coming to games, practice, calling on the phone. It was always my goal to play pro too while it was my parents goal to send me off to school. I started to think go pro and forego college after a good spring. When draft day came and my name was not called as high as I hoped, that had to have been the biggest "downer" day of my life. It takes the wind out of your sail when you get your mind set for something that doesn't happen.
My advise is to be aware that it may happen to your son and talk about all the possibilities that "might" happen prior to draft day. The bottom line, it is impossible to guess what might happen as far as the draft and it could lead to some big dissapointment that you will need to deal with later.
Brn2hit - great post.