Tina,
The ladies are doing a great job of helping you talk through your options!
I agree that the jump from Beyond to Preparing Hearts is very large, and it wouldn't be something we would normally recommend, unless you were thinking about only skipping a guide with your oldest to get him more accurately placed if that was needed.
That is an option you could consider, which would mean placing your 10 year old in Preparing and your next child in Bigger Hearts.
If you don't desire to do 2 guides, then it is a better option to place both in BIgger Hearts and use the extensions.
I agree that it is a good idea to have your older son read his own history and science, just doing it in a different place and earlier in the day than where and when you are doing the reading aloud of those same areas for your younger child. I wouldn't recommend having your older child read aloud the texts to your youngers, as he will then lose out on the benefit of reading his own material silently, which requires a whole different set of skills than reading aloud requires. The skill of silently reading to oneself and comprehending what is read is the skill we are wanting an older child to get. It is also much more difficult to read a history or science book than it is to read for pleasure. The vocabulary, sentence structure, and reading level is much higher in history and science books, and these types of books also require a higher level of comprehension to understand what is being read.
With his age level in mind, it is likely time for him to move toward doing this on his own, if he hasn't already.
Another needed skill to cultivate with an older child is the skill of reading and following lengthy written directions. This is another skill that your older child can work on as he reads and follows as many of his own directions from the guide as possible. Then, you could do any follow-ups that require the teacher together.
I would definitely work to cultivate these skills in your older son this upcoming year, and the thread on how to make Bigger more independent will be of help to you as you do this.
Otherwise, you could ponder moving only your oldest up to Preparing Hearts and having him do his own history and science readings there instead, but this would require running two guides. With the ages of your children, and with what you've shared so far, I'd lean more toward combining in Bigger Hearts. I think you will be pleasantly surprised about the depth and level of rigor within Bigger!
Blessings,
Carrie
It is the later part of American history, and Beyond only does the first part. It also transitions dc into doing more writing. Here is a link that may be helpful...