Crystal,
I have been teaching my kids for over a decade, following CM methods more often than not. My oldest has really struggled with writing, which I believe has held back my others. I finally feel like we are in a good place with writing. One thing that has really helped is to have a separate composition lesson, apart from their regular books & narrations. I choose a short passage, and they follow up with a written narration. Aesop’s Fables is a perfect beginning place. I plan on gradually increasing the difficulty of the passage as we go. I’m using some of the early AO/CM readings like Fifty Famous Stories Retold, Stories From the History of Rome, fairy tales, folk tales, mythology, etc. We also narrate after our school readings, but focus on oral narrations for those.
Since my older kids are in high school, I also plan on covering some additional writing styles towards the end of the year. Narrative style is covered through narration (telling a story). That leaves expository (inform/explain), descriptive (describe, make a word picture), and persuasive (opinions and persuasion). We can also eventually work on letter writing formats, play writing, and poetry. My plan is to have one narrative style narration and one additional style narration each week.
One thing that helped my oldest is IEW. They do a Key Word Outline. They pick 3 words from each sentence of a passage. They write the words out, each sentence’s key words on it’s own line of paper, then they rewrite (or retell) the passage using just the outline. It took away the blank page fear that was crippling my daughter’s writing abilities. That was her biggest issue—not knowing what to say. This might also help your son with ordering and organizing his thoughts. It doesn’t make for the most creative writing, but I think this method does have it’s place!