Wow there is a lot to read through here for someone just chiming in! I have come to really enjoy a ton of posts by Coach May, Cabbagedad, and many of you on the site, and the advice in this thread is great.
I am a high school teacher (though not a coach thank God) and I shoot as straight as I can with parents whose kids struggle. The biggest situation I run into is that the kid is just not all that interested in getting decent grades, or is not willing to work. With those kids whose parents "snowplow" the obstacles away for their children, I will typically ask them what they think will happen when their kids goes off to college or enters the real world and mom or dad are not there to help anymore. I will tell them about the valedictorian of my high school that flunked out of college his first semester because he didn't know how to do things or handle adversity himself.
I hear students everyday in my classroom talking about how coach only moved that kid up because he is his favorite, or how so and so is not "that good", or (insert excuse here).
I have a freshman, and my take is that it is all on him. I can try to help guide him in some key areas (and this site is amazing for that) but I have always told him that: if he is not talented enough, does not love the game enough, and is not willing to work hard enough then he may as well just have fun with it and take what he gets - because he will never be good enough to play at a higher level anyway.
Take these peoples' advice. Let your son fail. Make him be his own man.
I am much more concerned about what type of man my son will be at age 30 than "if" he gets to play a sport in college or not. Go google how many MLB guys realized their dream and played in the show for 2-3 years, and then see what they are doing now. The same things you and I are doing. Teaching, selling cars, running small businesses, coaching, working in the corporate world, etc.
I always try to keep this in mind - none of this crap is going to matter in 5 years anyway. Everything is going to work out as it is supposed to.