I see from previous posts that you've been trying to figure this out for a long time. I'm trying to be practical here, so please keep that in mind.
First of all, I wouldn't be too concerned with the 4 year old when you have others that really need the education at this point. In our state kids aren't required to formally be enrolled in school until the age of 6. How is it in yours? I would worry about the older kids, and then try to fit the 4 year old in when you have their situation figured out. Plus, I also recommend Leap Frog DVD for letters and sounds. They're fun, the kids learn, and it will free up your schedule for 30 minutes. Hey, that's something!
For starters, I wouldn't have all the kids start their programs at the same time. I would work my way down from the oldest to the youngest. I find routines to be very helpful. From what I understand, CTC is mostly independent. That will aleviate some of your stress from a teaching perspective.
Once everything falls into place with your oldest, then I would concentrate on your 9 year old, who falls into Bigger. Will you be adding the extension package? If not, that will really cut down on the time. For example, if your 9 year old does Preparing to Build English 2, that probably won't take more than 10 - 15 minutes. A lot of the required subjects are very thorough, but not very time consuming.
We just finished up LHFHG with my 5, 6 and 7 year old. My 7 year old also did 2nd grade work also, but I wanted to keep them together for convenience sake. This is an excellent program, and it only takes about an hour and a half. Would you consider starting your 6 year old with this program, just for your own sanity? As long as your child is working at his/her own level in phonics, reading and math, the rest of the program is completely enjoyable. The Burgess Thornton books are a perfect "starter" for narration. Each chapter begins with a review of the previous one, and they are great for teaching character. My children loved these books.
LHFHG would simplify things, but if your child is "ready" for Beyond, then don't mind me. It was just me trying to be practical and helpful. I have the Beyond and Bigger manuels, and I see how each one increases in expectations and work levels.
I think it is possible to coordinate 3 - 4 programs, although it will take some effort. Once you are able to get each child situated in their respective program, I think it could be managed.
Just my 2 cents.
Best wishes.
Joy