Hmmm. I think obsessing over the 'but I couldn't get there after 11pm!' thing is a bit telling.
It's not a great idea for dc to be picked up from residentials because of anxiety in the middle of the night, anyway. The idea is that you cheerily wave them off without suggesting that this might be a thing. Teaching staff will cope with the occasional upset.
I'm perhaps a bit impatient with this sort of wudgering because I'm a teacher myself & run lots of residential trips, but IME 9 times out of 10 problems are parent problems.
(obviously some dc couldn't, wouldn't, shouldn't go on a trip of this nature because they absolutely hate the idea. Fair enough. But I'd be giving reasonably robust encouragement to any of mine if they just didn't fancy it).
Having said all that, if you disagree that's cool. I definitely parent on the 'better drowned than duffers, if not duffers won't drown' end of the spectrum!
In which case, bollocks to meeting the HT. Just send a polite email explaining that your dc does not wish to go & your parenting policy is to accept that, so he will not be participating, & you are happy for him to have alternative provision made for him in school, or to Home Ed that week. Job done.