I'm a lifelong stutterer and I recently graduated college. The social aspect was challenging at first but it really helped me that I dive right in and got socially involved. Its important for your son not to socially isolate in college, especially at first. It seems like a daunting task but your son should know that it gets easier for a stutterer and college, especially if he surrounds himself with people who lift him up and don't care about the way he talks, which is bound to happen over time.