Was the William H. Macy character part of the con?

In the David Mamet movie House of Games, Mike (Joe Mantegna) lures Margaret Ford (Lindsay Crouse) into their circle by proving a small con at the Western Union Office. He explains that the basic idea of confidence games is that the con man gives his confidence to the victim, such that the victim will hand over his money to him, a total stranger.

William H. Macy, playing a Marine headed back to Camp Pendelton, promises some money to Mike, who he thinks is a stranded former Marine and wife waiting for emergency cash because they had been robbed. However, I wonder if the scene was pre-arranged, acted out just for Margaret's benefit.

It would give Margaret the idea we were allowing her to have inside information from the start - enough to make her confident she was leading the confidence game rather than losing her fortune. For this to be true, Macy's character had to be a bit player in the con. Mike refuses the money offer from Macy, and then walks Margaret to the hotel for sex, followed by his next "bit" of the night. The timing of the Marines in conversation, followed by the walk to the hotel, seems timed precisely to arrive at the hotel just as Mike's partner con man descends from the elevator.

So, was the Macy character part of the con?