What is the function of the work's minor characters?

In Graham Greene's 1954 short story, the main character is Trevor, or "T," as he prefers to be called to downplay his "posh" upbringing.  Blackie could be considered another major character, since it is he that T has to challenge to gain control of the Wormsley Common gang.
The work's minor characters, then, are Mr. Thomas, called "Old Misery" by the boys; Mike, a nine-year-old who has been intimidated by the other boys to remain quiet; a boy named Summers; another named Joe; and the lorry driver who inadvertently pulls down the remnants of Mr. Thomas's house. Mike, Summers, and Joe function as gang members who go along with the decisions made by first Blackie, then by T. Their role is to assist in the destruction of the house without requiring a rationale or a reward. They have either been conditioned to mindlessly follow others, or they choose it.
Though Mr. Thomas feels like a victim, and most sensible readers would agree that the boys victimize him, he is not T's —the house is. It isn't hatred or revenge against him personally that propels the boys to their destruction. The lorry driver—or more accurately his lorry—is a tool used by the boys. He has no investment in what the boys do, nor does he have any genuine sympathy for Mr. Thomas.