If you haven’t been following along in the Parents of the HS Class of 2024 thread, you might want to read some of the latest posts from about here on: Parents of the HS Class of 2024 - #4279 by evergreen5
…and at least one of the schools on your list is mentioned as doing this.
The schools in the low probability bucket have a ton of demand from highly qualified students, and they definitely expect a lot from the applications. I would not have your son chew off more (in the way of apps) than he wants to chew. Generally, public schools and less selective schools will have lower requirements with respect to essays (i.e. for many, the Common App is sufficient, or there’s one “why us?” essay).