Welcome to FlyerTalk.

Good thing you're thinking ahead. I've seen these things go sour - I booked my nephew's fiancée a room at a hotel near JFK, I called in advance and they denied her the room (charged me anyway initially).

Your guarantor could have added the name of a second person on many hotel websites, and included a note. He should tell the hotel and preferably get a confirming email - whether he calls or finds an email to write.

Which hotel? One of our members with experience at that property might be able to chime in.