Technically it was a train, and they were experiencing a transcendent connection across time with their older selves, in a deliberately unsettling and transgressive scene meant to evoke the rawness of adolescence being laid bare before the worst cosmic horror -- an eldritch carrion-eater who feeds on destroying the souls of children -- as a way of reclaiming strength from vulnerability. At any rate, depiction is not endorsement.
But yes, considering how many actual adults misinterpret and mischaracterize that scene, I don't recommend that particular book to children -- not because they'll be damaged by it, but because they won't have the wisdom of age to understand it.
Well that's pretty rude. Kathy Bates is an attractive person and doesn't deserve this kind of slander.