Can he step directly into farming and make it? Sounds like it.  But I really think it would be in your son's best interest to get away from the farm a little.  I don't know about your area, but here the junior college system has programs designed to work around the farming season.

He needs to understand that much of what you learn at college is not in the book learning.  Social interaction, being responsible for your own decisions, hearing new and different ideas, these are every bit as important as the book learning.  Especially if he has been home schooled for 4 years.

If you can get by without him for a while I would strongly encourage him to get either an off-farm job or a job working for somebody besides Dad for a couple years.  My junior college was an hour drive from home.  The first semester I was there I worked part time for a local implement dealership as a shop boy. I worked 10-20 hours a week depending on needs and my schedule.  Bought my first Snap-On tools while working there.  Learned more than I realized at the time.

The school had an ag internship program designed to put the student back on the home farm in a full time employment setting.  Because I was getting married and my wife was in school, instead of coming home I worked for a year on an area farm as a hired hand.

It was probably one of the best parts of the program. I learned there were other ways to do things than we did them.  I didn't come home and make big changes at once because of it, but looking at my operation today I can see how it has influenced what I have done.

As others have said or hinted, I kind of regret not going on to get a 4 year degree now.  Not for the paper to hang on the wall, but for the knowledge.  I would encourage you to REQUIRE he get more education and experience before coming back to the farm.

As to how to bring him in ... I don't know you can give us enough information to offer specific advice.  We can toss out ideas and our experience, but it is going to boil down to how you folks can work it out.