Hi Kristen! From what you've shared so far, it sounds like your ds is doing well with PHFHG. I would continue to help him become familiar with the PHFHG guide by using it as his own. He should be reading his directions in the guide, getting out his materials, completing his "I" work independently, his "S" work with you getting him started but finishing it independently, and his "T" work with you by his side. He should also be learning to hand in his work and clean up his materials as he works through his plans. These are the skills that he will be able to acquire more and more as he works through the guide, and they are what makes it possible for you to come alongside your oldest dd and younger dd, both of which need you more now.
For your oldest dd, being able to manage time and work on task are skills to be learned that take some dc more time than others. My middle ds has needed more time to grow in these skills than my oldest ds did. I think this is fairly common.

I would back off to doing Bigger Hearts half-speed with your dd, doing the left side of the guide one day and the right side the next, and come alongside her to help her learn these time management and attention to task skills. It helped my ds for me to print off the approximate times each box should be taking in Bigger Hearts, and schedule his work time accordingly, setting the timer for each box and working alongside him to help him realize about how long things should be taking him. Here is a link to those time allotments:
BHFHG time it takes:
viewtopic.php?f=12&t=702
You can easily choose to do 1 Storytime with everyone instead of 2. That is an easy way to economize time. I am wondering how there is an hour of together work though? What are you doing with everyone for an hour? This actually may be adding time to the day as well. I have found teaching blocks of time seem to really help me teach multiple guides. I used to begin by teaching my littlest son first, but this year I began teaching my oldest ds first, and letting my younger 2 dc just play with one another. This has worked so well for us. It gives my oldest ds more time to do this work, and he has the most work to do, so this fit us well. I think it's a good idea to try some different ways of setting up your day to see what works best for your family. For some families, beginning with the littlest works the best, for other beginning with the oldest works the best, and this can change from year to year based on the ages of the family over all.

Here's a copy of our schedule, in case it could help you out somehow:
With your dc being just a few years apart, you could go back to the combining them, but I am thinking that separating them has shown some important skills your dd would benefit from gaining. If your dd is struggling with completing the work in a timely fashion within Bigger Hearts, I am thinking that PHFHG will just be more of a struggle. It also sounds like your ds is ready to fly and feels frustrated waiting for younger sister to finish. You will know best what to do here, but I think exploring the separate guides for a bit longer is worthwhile. If you get a chance to share how your day is going more specifically, we can brainstorm in more detail too! It is an adjustment to do multiple guides, and I have found a schedule at that point is a real benefit.

I hope something here helps, but just remember starting anything new takes time and requires some transitioning. We can help with the details if you get a chance to share more of your day's happenings. HTH!
In Christ,
Julie