Thank you so much for taking the time to type out answers to my questions!
It helps so much to get a fuller picture of what each child has had and where he or she may fit best. From what you've shared, it does sound to me like your 12 year old would fit well in CTC. You will need to plan on some time to train her in using the guide so that she is able to know what to do for the 'I' boxes (before she'll truly be independent). You may even want to start her a bit earlier than your other children, just to get her in the groove of the guide.
I'd lean toward having her do English 4 or 5 at half-speed as planned in CTC. You'll want to be sure that she does much of the lessons orally with you so that the written work in English doesn't get to be too much.As far as your 8 and 10 year old go, I do think that while they both read very well, there are other skills across the curriculum that it sounds like they still need practice to develop. As far as your 8 year old goes, I think Bigger Hearts would be very good for him. It would move him into more written work at a steady pace and give him a foundational exposure to grammar which he needs. I would place him in English 2. Your 10 year old on her own would fit well in Preparing. Based on what you have shared, I would not put her in CTC with your older child as it would be overwhelming.
So with these thoughts in mind, I would lean toward combining your 8 and 10 year old instead. Typically when we combine two kiddos, we lean toward combining with the younger student in mind and then extend for the older. That would mean placing both kiddos in Bigger, while adding the Extensions for your 10 year old. The areas of written work (across the curriculum) and grammar especially hold your 8 year old back from combining in Preparing with your 10 year old, which is why I'm leaning toward Bigger instead.
While you could modify the writing areas to allow your 8 year old to place in Preparing, I wonder whether you would then continually be modifying the writing for years to come and never fully reaping the benefits of using the guides as written. Typically, it takes an 8 year old who is very strong in all areas of language arts and math to thrive in Preparing, as age 8 is the youngest age for which the Preparing guide is targeted. This is why I keep coming back to Bigger with extensions as a placement for your 8 and 10 year old, as it will be something you can truly expect both students to fully do. Only you can know whether your 8 year old could handle the writing requirements in Preparing and also handle the writing requirements and amount of independence for CTC the next year. If you think he could handle the written work as scheduled in Preparing, you could still ponder a combination of the 8 and 10 year old in Preparing.
In both programs, the readings will be very short, Charlotte-Mason style, asking a child to dwell with a book over a longer period of time to really "live" with it. This slower, more thoughtful reading may be a shift from what your kiddos are used to, yet it reaps big rewards when combined with the follow-up skills scheduled in each guide.
So, I would encourage you to look as much at the skills as at the reading levels and reading assignments when placing your kiddos, as the skills are key to correct placement. I would also lean toward DITHR for your older 3 kiddos once you have gotten underway successfully with your other HOD programs. This placement would mean that you would be teaching LHFHG to your 6 year old, Bigger (or Preparing) to your 8 and 10 year old, and CTC to your 12 year old. What are your thoughts?
Blessings,
Carrie