Here's why:
* The family dynamic: Bob Ewell was known to be a controlling and abusive father. It's likely he would have kept his children close, especially in the wake of his humiliation during the Tom Robinson trial.
* The context of the attack: The attack occurs at night, after Jem and Scout leave the Halloween pageant. There's no mention of any other children being involved, suggesting they were not present.
* The purpose of the attack: The attack was a direct act of revenge against Atticus Finch, aimed at punishing him for defending Tom Robinson. It's unlikely Bob Ewell would involve his children in such a dangerous and vengeful act.
While the book doesn't provide a definitive answer, based on the context and the characters' personalities, it's most plausible that the other Ewell children were at home with their father on that fateful night.