Christie, would it work better to break it into smaller chunks for starters? Maybe you could assign your 9yo to listen for any commands to obey and your 6yo to listen for any sins to avoid. You could even read the chapter ahead of time to see which of the GOAL aspects are most obvious and assign just those to individuals for listening.
You could also model what they are learning to listen for by stopping after you read one of the aspects and drawing attention to it, “Oh, that’s a promise we can grasp!” and asking the children how they want you to write it in the book.
In other words, this pass through the epistles may not be comprehensive and cover all the GOAL aspects in all the chapters; that’s okay. This pass through may be a learning time to help the children progress in identifying applications as they listen.
Just some thoughts. 
