Walkerr, your son has a one-year "grace period" after his HS graduation that he can delay full-time college enrollment, and still play on a travel team in organized competition without harming his NCAA eligibility. He won't start his eligibility "clock" as long as he doesn't enroll at a college as a full-time student. The downside is that he won't be eligible to practice with the college team (if the part-time classes are at an NCAA institution) if he's not in a full-time course load.
BOF mentioned less than 12 units, and RJM referred to two courses. Both are on the right track. The key is that your son NOT register for whatever that particular college considers to be a full-time course load.
Here's an example of a mistake some athletes make - an athlete signs up for a course load considered to be full-time at a particular college. The athlete attends the first day of classes at the college with his full-time course registration. On the second day of classes, he drops a class and is now considered to be a part-time student. In this scenario, the athlete has started his NCAA eligibility "clock."