"Are the children ready?"
Translation:Est-ce que les enfants sont prêts ?
Inverting verb and subject to form questions is only done with a pronoun. This means that to use inversion, you have to insert the appropriate pronoun and invert that with the verb.
- Les enfants sont-ils prêts ? = Are the children ready?
A word for word translation from the English does not work here because it violates the French grammar rule.
Because "sont" is the verb "are".
"Est-ce que" is not a verb and is simply a tool to turn a statement into a question. You slap it in front of a sentence and it becomes a question.
- Les enfants sont prêts. = The children are ready.
- Est-ce que les enfants sont prêts ? = Are the children ready?