Amy,
Another mom here who is LOVING Little Hearts with my kiddos!

It truly does work with quite an age spread of kids due to the way Carrie has written it. I'm using it for the 2nd time with my 5 year old right now. He's a normal 5 yo, fun-loving, wiggly, little boy.

And we're having a fabulous year! We also had equal succes with my daughter as a new 5 year old.
The Burgess books do take the most getting used to as far as listening goes, but I think that the majority of moms see huge growth in this area from the beginning of the year to the end.

My kids have LOVED the Burgess books! I always make sure to mention before I read that I have some questions for my good listener(s) when the story is done, and I can't wait to see how well they've listened. Or..."today you're going to get to act out the story for me when it's done"...or..."Wow! You get to narrate to me today after the story just like Grant does! Are you old enough for that already??" If there's a word mentioned in the follow-up box I'll let them know that they can be detectives and listen for the word "___________" while I'm reading and see if they can tell me what it means when the story is done. Now, these ideas aren't really mine.

They're from reading the narration tips in HOD's guides as we've gone on. I've just found that saying something like the above lets my little listener know that they're going to be telling me about it when we're through reading and it encourages them to pay attention for the short time that the reading takes.
I have never thought that the history reading seemed to be too advanced for my 5 year olds either. The readings are very short. We usually begin our history page with the rhyme that gets us up and moving and introduces the theme for the week in a very age-appropriate way. I know that the story Bible takes you through a good portion of the year for the history page. Then the follow-up activities for that page reinforce the theme with great 5-7 year old ideas!
I think that you'll have a GREAT year with your 5 and 6 year olds in LHFHG!

If it seems like it's too much for the younger, just slow down the left page and storytime a little. Like 4 days per week. Or half speed. (I know there are threads here about "how half-speed looks in your home". I shared how we did that when I had our 3 yo tagging along with his sister for a year.) You could always keep the older one blazing along with the basics of phonics, math, and fine motor skills and give the younger one a day off.
exodus4 - If you've been telling your little ones that their answers/narrations need to be a certain way, do you think it's intimidating their answers? I am getting from your post that they are really having a hard time comprehending or telling you anything back right away. (And the moms here have done a great job of sharing some experience and ideas with you about that!) But one thing that jumped out at me while I was reading this was that one of your kids was looking int he guide to see the key idea before you read so that they could have the "right" answer when you were done. Maybe you could mention that there are A LOT of right ways to tell you about the story. (I know that I was scared to answer questions or try new things when I was younger for fear of being wrong.

) You could illustrate that by asking them each to tell you about a shared family experience - such as a trip to the park. You could ask you son to tell you about his afternoon, for example. Then turn to your daughter and have her do the same. After they share point out that they both were "right" in sharing about their afternoon with you, but their "narrations" were quite different because they remembered different things and different things were important to them. Then point out that it's the same way when we read from a book or watch a movie. We can all tell what happened in the book, but our stories won't be identical because different things will stick in our minds as important. But the main ideas should still be the same.

Does that make sense?

Kathleen