RE: Stanford/Showball/Headfirst choices: I'd think about going to two, but I think all three is overkill. I know kids who ended up at NESCAC schools after going to only one of those showcases. Save those $ for a couple of camp visits at schools that show serious interest and your son is REALLY interested in.
Timing: Covid has messed things up for D3 ED commitments to HA schools. Both my older boys ('17, '19) were able to attend camps at top choice schools in October, visit classes, etc and then make their decision. My youngest ('22) has had no such luck. Some schools have wrapped things up by Labor Day while others are giving kids until Nov. 1 to commit. Very frustrating because it means having to make decisions without the advantage of visiting schools while students are there. This is critical I think because the school vibe is a major component of "fit." Don't underestimate the importance of fit.
Location: We're in the west. Older boys went to NESCAC and Centennial schools. One kid loves his school, the other one tolerates his. The latter says the kids at his school are clueless about partying, act geeky, and make dumb decisions that he says he made when he was still in HS. He's staying for a good reason, the academics, but I'm sad that he's not having more fun.
Good luck. You're asking great questions and getting great answers (not mine, but the other ones are awesome 
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