Problem here is you are talking about serving strategy for your kid.
I'm talking about serving strategy for a guy who peaked 20 odd years ago.
If you get used to my normal moderate toss, and then I throw one in with a Tanner toss, you would not read it in time, even though you are a 5.0 level player. Once you've seen it, you start to hone in on it, of course.
I've experimented with this idea with an old fart who beat me bagels. Mostly used my regular moderate toss, but on game points, used my lower quicker toss action. Worked wonders, I won the important point easily 5 out of 6 times I tried it, and the one that failed, I volleyed into the net, my fault.
As for more into the court, I don't believe in that at all. OTOH, I don't hit serves at 60% speed, then try to bust one past the opponent. All my first flats up the T are hit with my max speed, whether "80" or 115, whatever. I vary my spins and placements also.
Maybe my structure in that idea offsets my flexibility to toss higher and lower.