I'd like to book a night at HSW for my parents without me staying and have them receive the Diamond bells and whistles without paying the standard rate. If I check in and give them the room key would that work? I have no idea if they'd get queried at the lounge because of an age discrepancy. Does your official +1 have to be registered by name? I'd find it a bit weird checking into a room with my mother that has only a King bed!
I guess the other option is I book 2 queens, say there are 3 of us and hope we all get the benefits extended and then I don't actually stay the night.