sockknitter,
Thank you for being so gracious to share about your kiddos with me! It really does help me to see where they would fit better.

I am thinking of one possible option that would really help you give your daughter a strong year in the 3R's, while also having all your kiddos hit American history. To do this, you could combine all 3 of your kiddos within Bigger Hearts for only the left side of the plans (Learning Through History), using the Extension Package for your daughter. This is a good option, even though your daughter is beyond the target range of Bigger Hearts, as your kiddos really should have a year of American history.
Doing Bigger Hearts with all of them for a year would also allow you time to delve into Drawn into the Heart of Reading, which will be important especially for your older daughter as she'll be needing the literature study skills that DITHR provides as she nears high school. I would also recommend taking a look at Rod and Staff English for your daughter to up the level of her English and writing skills. This would be very helpful for her as she heads into her middle/high school years.

You would then add the right side of the Creation to Christ plans for your daughter to give her a higher level of dictation passages, a schedule for Rod and Staff English 4 (if you choose for her to use that), a reminder of when to do DITHR, 2 lessons a week with Write with the Best, Primary Math 3A/3B, and the CTC science. The only part you would omit on the CTC right side of the plans for her would be the Geography of the Bible Lands and Genesis Finding Our Roots and the poetry box.
The other possible option would be to place your twins in Bigger Hearts and your daughter in Preparing Hearts for all areas. This will take a bit more doing on your part and would require running two programs. Many families easily run two HOD programs, however in this scenario, you would need to train your daughter to be quite independent with the Preparing Hearts guide. We have done this with our sons, but it does take some training. Only you would know how well your daughter would be able to read written directions and work more independently.
One last consideration would be combining all of your kiddos in Preparing Hearts and using the Extensions for your daughter. I am a bit concerned about this option, as I fear one of your twins would be pulled along in this option.
Any of these scenarios would work and each has its own strengths. I'd love to hear your thoughts if you get a minute.
Blessings,
Carrie