There are plenty of hotels in HK that do not require key card access. For convenience factor, you can book a room at the same hotels where the HGs are. That solves everything since the HGs are at the same hotel, they are comfortable there as they are guests, and there is no way they will forget or get lost on the way to your room, lol.
Unfortunately, I can't stay in those hotels as my company requires me to stay in approved hotels. That being said, I guarantee that 5-star hotels that I've stayed at are discreet and more than ok to let HGs up to your room. They call your room and confirm that you're expecting a friend, and once you say ok, they let them up. No muss, no fuss. I've never been stopped or reprimanded either.