Start sending emails now!! If he's too busy with school and his HS team, you send them from his email account if you have to (write as if you were 17). It's not too late for HA D1 or D3.
Do not solely rely on getting noticed at a Showcase, it's a pipe dream to put bluntly. Same with tournaments...your son needs to be on their radar so they come to watch him.
I have many examples of my son getting recruited/calls/texts from coaches who were at those Showcases, while we were home saving thousands of $.