This is something I'd ask my Concierge to do. They should be able to note GoH on the reservation, and send you an email confirming that's been done, as I don't recall it showing up when viewing the reservation online or in the app. It wouldn't hurt to follow up with the PHT directly a couple of days before you arrive, too, just to make sure your parents are properly taken care of.
Thanks so much. Haven't unlocked a Concierge yet, but I'll see what I can do. You're right - best to get confirmation. Thanks for your help.