Heidi,
I agree that juggling students from high school down to those just beginning to read can be a wide range and make for a very busy momma.
We have that at our house too! Add to that the fact that some of your learners have challenges in the reading department, and this will add time to your day no matter what curriculum you use.
In pondering your situation, I will share that in our guides from RTR on up, we do plan the choice for storytime to be read either by the student or by the parent. I'm thinking that your older daughter could be reading her own storytime in RTR to help you in that area. Depending on the difficulty of the history and science material for your older child, hopefully she is also able to read some of that material, saving you from having to read it all to her (which adds significant time).
As far as your son in Bigger Hearts goes, we do typically recommend that you only do one storytime with your students. So, if you're doing more than one HOD guide, we wouldn't be planning for you to do multiple storytimes each day.
With that in mind, you'd want to choose one set of storytime books to read aloud to your group. It is likely that your older daughter should still do her own storytime if possible, or else the extensions to raise the level to whatever you feel is appropriate to her though. If you're reading her Storytime to her though, then you'll need to reassess so you don't get overloaded.
Another thought I had is that we typically wouldn't recommend that you do back-to-back guides such as doing Beyond and Bigger Hearts at the same time. If you do have to do this kind of situation, it is likely that the teaching load will be heavier than you'd like (when keeping in mind that you are having to do so much yet with your older learner in RTR due to her unique needs). Usually having a child in RTR would mean that you'd be gaining some time back to work with your youngers. I can understand that the learning challenges of your older student makes this less feasible, so I'm thinking that the combination of time spent with your older, along with trying to do 2 programs back-to-back with younger learners who are still trying to grasp reading is making your day longer than it should be! Likely, some of this affects how well your younger child is doing in Beyond.
A couple of thoughts I have are as follows:
1) If at all possible, I'd move toward having your older daughter read as much of her texts for RTR or for Revival to Revolution on her own as she possibly can. Even if she doesn't have terrific comprehension, taking from it what she can is a goal.
2) You'll likely be reading the texts to your Bigger Hearts child as he moves into Preparing Hearts, but Preparing Hearts is a 4 day plan so that should help some. This will potentially be where more of your time is, but I would really try to have your son read the Independent History Box readings and the science readings on his own if at all possible. The science readings are especially short. You could even do Preparing Hearts at half-speed for awhile if needed to ease into it. But the skill progression from Bigger Hearts to Preparing Hearts is such a good one that you will reap the benefits as you move into Preparing, which should make it less intensive than Bigger Hearts.
3) I would keep going in Beyond with your younger child and just work your way through it whether he seems to be taking it all in or not. While you could easily add colorful books and images to try to match his visual/spatial personality if needed, I wouldn't work terribly hard in that area, as at the age he is he'll also need to be developing his auditory skills and moving toward comprehension in books without pictures. The readings in Beyond will stretch his auditory skills and help him develop strengths in other areas that will be of such help to him as he moves up through the grades.
If you do continue on with Beyond, I would likely have the older brother who is moving into Preparing Hearts listen in to the chapter book readings from Beyond with his younger brother for Storytime. In this way, they could do Storytime together. You would then omit the Storytime for Preparing Hearts but instead be sure that the child in Preparing Hearts is doing the Independent History Study box and the Science Box, as these will be the more important skills for him.
As your middle child moves into Preparing Hearts, and hopefully a bit more independence, you may find Beyond a better fit overall in your day.
4) I would work to be as consistent as possible with Beyond and systematically move forward with it every day. It is amazing how much progress those little ones make when you just work the guide, instead of continually pondering whether it fits the child. I share this because I spent years switching through things with my oldest son, always looking for the perfect fit, yet the greatest progress he makes is always when I just settle in and do what I have for a whole school year. The skills are what is needed in a steady progression, and they are often what end up lacking when hopping from one curriculum to another or when being sporadic in our teaching. Yet, it is the skills the kiddos need to move toward more independence and a higher level of learning. With this in mind, it honestly would be better to just head through Beyond, and then evaluate again when you finish to see the progress. The lessons are short, the readings are short, but the skills are all there. Sometimes it isn't readily apparent until you are almost done and looking back.
As the momma, you will know far better than me what is right for your family and if the Lord brings you to change curriculum, He will also give you peace in that. I just wanted to talk through some things that I've found that may be of help to you as you ponder.
Hopefully, some of it will be of help! I know you must be weary as you get closer to the end of the year, yet I want to encourage you that it sounds like your kiddos have made good progress overall. It's important to take time to feel good about that.
I think in the looking back, you will see strong gains and a good steady progression of skills that if you continue on with HOD will make your life easier and easier as you go. Each guide has a rhyme and reason to it that prepares the child for the next guide in line. If you give each guide a year, I think you will truly see its fruit.
I pray the Lord will show you what He desires for your children, whatever that may be, and that He will give you peace in Him as you journey.
Blessings,
Carrie