An adaptation of the Catechism for Young Children in modern English.
Question: Who did Christ obey and suffer for?
Answer: Everyone the Father had given him.
Question: For whom did Christ obey and suffer?
Answer: For those whom the Father had given him.
Again, children don’t care if you refer to an object with “who” or end a sentence in a preposition. And, “For those whom” is simplified to “Everyone” – which also makes the answer closer to the language of John 6.