As I mentioned before, scholarships are renewable year to year. The NLI doesn't extended itself past the first year. There should be no verbage in the NLI regarding sophmore-senior year as far as I know. I am not familiar with 4 year guaranteed scholarships, which are handed out pretty sparingly.
All the NLI does is guarantee a "place" for you on the roster next year. The rest is up to your son to give the reason for the coach not to let you go.