time for tea and meet the in-laws
So on Sunday morning, fighting his hangover, he calls her to invite her to lunch with his family. Then he informs the others that he's having a girl over to meet them, and endures the somewhat suspicious looks this rather unprecedented act earns him. He calls down to room service for a decent lunch to be brought up, and even bothers to put on something not what he passed out in the night before.
And at twelve-thirty he is ready and waiting for her in the lobby of the hotel.