For a 2019 it doesn't really matter which date. But, before you sign up for any showcase (HF or Showball) your son should email the coaches on his target list to find out which specific showcase they'll be attending and exactly which coach will be there.
More importantly, will your sons measurables and talent be in standout mode when he does show up? AS a 2019 he has to give the coaches a reason to look his way while they're focused on 2018's.
At the showcases your son will have a chance to meet a target list coach for a minutes and allow the coach to match a face with an email. If, your sons play and measurables standout, the brief meeting with the coach could be an actual conversation. This will be helpful going into the junior year, and then your son could be one of lucky phone calls or texts on Sept 1st. Even if that were to happen, the college will not engage further before they hear a sufficient ACT score.
It would aid your showcase and camp decision making if you had a good sense of where your son projects and what are his measurables. If your son projects at D3 and your sons interest is academic D3's you have lots of time. This the golden opportunity to focus on development, strength and speed to help your son prepare for junior HS spring ball, rising senior summer tournaments, and the rising senior summer showcase circuit.
Bit off your specific question, but key things to be aware of....