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 $.
I would not ghostwrite emails for my son. If he thinks he is to busy in high school to "own" his recruitment he will get killed when he shows up on campus.....it truly is a fulltime job.
I also think sending emails without verifiable stats and good video will yield poor results. He should spend time now identifying 20 to 30 schools of interest, acquire contact info, etc and get ready to go as soon as you have stats/tape....getting stats/tape should be the priority