Starting in Middle School – Where to begin?

I am new and researching this method to begin with our next school year (beginning July 2018). Currently, I have a 9 year old son in 3rd grade and on track, and a 12 year old daughter who is technically in the 7th grade but is delayed and doing late 4th/early 5th grade level work. I realize grade levels are not of much concern in CM methods but that’s where I’m coming from. They were previously public schooled and my daughter’s delays are why we began homeschooling; we are in our 3rd year.

I am struggling with my daughter and how to approach things so she still gets a full history education by graduation. Technically, she will be an 8th grader (by age and current year progression) when we begin, giving us only 5 years of the CM method. I’m not sure where to start with the history curriculum. I’d like to start at Genesis and work through chronologically. However, doing so won’t allow her to study from the 6th volume and she won’t receive a modern history education. I don’t like that. I could start her over at 7th grade and keep her home another year and this would allow all 6 years to be covered. I think what gets me the most with this is her involvement with the youth group at church. She just started this year as a 7th grader. Everyone knows her grade. She is very shy and anxious around new people (we are fairly new to the church) and I don’t want to put that label on her as being held back in school. Again, I realize all this isn’t much of a concern with CM teaching but I’m trying to reconcile her social world with her school world and keeping her delays in mind. I need assistance thinking this through.  I hope all this makes sense.

I’m not worried about all the other subjects. We are working from where she is in math and moving forward at her pace. And we will start with Volume 1 of Enrichment. It’s mainly where to start with history/geography/bible.