Yes, the kid MUST play, despite the coach's desire to bench him. I'm sure that Bushref wouldn't agree with this either.
If the team refuses to comply with 3-1-1, you go to 5-4-1 because this makes a travesty of the game.
Rule 5 Scoring and Timing Regulations
SECTION 4 FORFEITURE, PROTEST, INTERRUPTED GAME
ART. 1 . . . The referee shall forfeit the game if a team refuses to play after being instructed to do so by any official. The referee may also forfeit a game if any player, team member, bench personnel or coach fails to comply with any technical-foul penalty, or repeatedly commits technical-foul infractions or other acts which make a travesty of the game. If the team to which the game is forfeited is ahead, the score at the time of forfeiture shall stand. If this team is not ahead, the score shall be recorded as 2-0 in its favor.