It seems that your son is everything that a coach would want. And for a prospect like that, a coach will down right tell you to come to his school. Since it is a D3 school, there are very little rules and regulations (nearly none) the coach has to follow as compared to D1s and in some instances D2s in regards to when and how to sign a prospect to the program.
And like others have said here, for a D3 you will not be asked to sign a NLI. Often, coaches will ask you to apply to the school in order to get you to sign the academic papers as soon as possible. But remember, you can always back out of any academic application you have made if another better offer comes in the mail.
Good luck