Thanks so much for sharing a bit more about your kiddos. In thinking through what you've shared, and keeping in mind your busy work schedule, I think it will be very important for your kiddos to be placed in guides that they can work through without requiring tons of extra teaching, help, and guidance from you (outside of what the guide already requires).
It sounds like your son is well-placed workload-wise in CTC for right now (even though he may be able to handle the content of a higher guide) and just needs to be accountable to do each day's work within a day. To help him do this, I would meet with him mid-morning to go over his work. Then, meet with him again near lunch to go over the rest. Let him know that he is to do what is assigned, without reading ahead. I love the idea that he enjoys his books so much he wants to read more, but when it makes him unable to finish the rest of his assigned work for the day... the positive becomes a negative. If he understands that he has to finish a day within a day, then he may do better with only doing what is assigned. I tell my boys that it is an obedience issue if they continually do their own thing rather than doing what is in the guide.
One other thing that may help with your schedule would be to have your son in CTC do an hour of school from 8:00-9:00 at night to get ahead for the next day. My two middle boys do this each night, and it really helps take part of the load off for the next day. They love getting up in the morning feeling like they have a jump start on their school. Their evening subjects are typically their independent ones, so I don't have to do anything with them at that point except make sure they are working during that time. Then, we check those subjects first the next morning.
Right now, to move up several guides in work volume would likely be overwhelming to both you and your son at this point. If you were going to move him up a guide, I would be inclined to move into RTR rather than Rev2Rev. But before considering any move, he needs to start doing a full day of CTC within a day for awhile. He also needs to be sure to do the 'I' boxes as independently as possible. You will still need to check the 'I' boxes and go over that material, but the work should be done independently first.
As far as your younger child goes, I may be inclined to finish Beyond at this point. Even though your younger child is turning 9, it would help to have the skills from Beyond before heading into Bigger. It will make Bigger less overwhelming for both teacher and student. If you feel Beyond is way too easy though, you can definitely head into Bigger instead. You will know best. You may just want to begin half speed then in Bigger at first. I would also look at the things you are using for reading, spelling, writing, and math with your younger child and add up how much time those are each taking. If you are adding a bunch of separate time-consuming programs for those areas, it could be that your time is going to those extra programs leaving you unable to get to the rest of Beyond or Bigger. If that is the case, you may need to consider moving over to more of the recommendations within Beyond or Bigger in those areas to get your time more in balance. The same could be true for your son, if you are adding on time-consuming programs in the 3R's for him.
Last, I would suggest that if you can minimize outside interruptions during school time that will really help. Keep your mornings until 1:00 set aside strictly for school. Try not to go off on bunny trails and stick to doing a day within a day of the guides if at all possible. If you can realize that your frustrations at this point stem partly from feeling like you're not steadily moving forward with the guides, then you can focus more on just doing what the guide says and then being done for the day. It can actually be a relief to let the guide be your gauge as to when you've done enough. This will likely help your son too, as right now he may not have the expectation to finish a full day's work each day, and he may feel like he's never sure what will be added or taken away from the day's plan. So, I would encourage you to just stick with what is on the printed page without adding or subtracting for awhile and see how it changes your school days. I am an adder by nature, and this was something I had to learn myself! I finally realized my boys just wanted to know what they had to do for the day, and then they wanted to do it and be done!
Boys need to know what the tasks for the day are. They are finishers by nature and do not want to constantly have more added. More is sometimes just more... not better.
I would encourage you not to worry about feeling behind and needing to jump ahead. There are so many good work habits that are learned within CTC that you will not be wasting your son's time in going through that guide. If you worked steadily through it for March, April, and May, then he would be on week 23 of CTC at that point. Then, we can take another look at jumping up to RTR or even Rev2Rev in the fall. Focus on the goals for your son of establishing good work habits, getting better at reading directions, being less distracted (perhaps your son needs to move to a quieter area while still being near you), and finishing what is started. We are working on those same goals right now with my own 14 year old son which is why these goals readily spring to my mind!!
While these goals will never be accomplished in a single year, progress is what we're seeking!
Believe me when I say I tell myself this daily!
Here is a link to my schedule, when I was using CTC and Beyond. Keep in mind this particular schedule of mine does not reflect the evening set-up time I mentioned (because we hadn't started it yet back then). Also, my schedule includes my two other boys, so it will be more convoluted than you will need. So, it may or may not help. You will likely also want to be done by 1:00, which is possible if your older son does an hour of school the night before. My boys are all done by 1:00 pretty much these days...thanks to evening set-up! Scroll down at the link to see my schedule: