I've had this "upgrade" before. Fine when traveling with my wife. Not so great when traveling with a friend.
I noticed that all of my reservations have "KING BED" as a request in the comments, and so I ask my concierge to take that out when I'm traveling with a friend and to make it clear in the comments that I need two beds.
I haven't had an issue yet - although I have missed out on some good upgrades because nicer rooms typically have one king bed.
Not sure what I'd do in your situation, but I wouldn't be happy.