Good morning, Liz! I know that things can seem overwhelming when first getting started, but HOD makes it easier on us busy moms than most programs.
I think just starting would ease some of your anxiety - I know I can stress about things to the point of my stomach being in knots sometimes, and if I just would have started, I probably wouldn't have stressed myself out so much.
Maybe this would be true for you too!
I think you have a great idea to start first with the little one - those little ones sure do want the mama first thing in the day!
I'd get started first with Little Hands to Heaven first thing sometime this week. To prepare for that, you could skim the first day of plans, put all of the LHTH books in a tub, make sure you have your art/school supplies at hand, and let the older dc know they may not interrupt you during that time at all (they can be in their rooms reading or eating breakfast - or anything totally independent away from you and the littles).
I think I'd just do LHTH for the first week, and I know you are going to get into that groove and love it. Here's an easy rotation for the LHTH boxes that we have used: Bible Story, Bible Activity, Fingerplay, Letter Activity, Music, Rotating Box (which is math, devotional, dramatic play, or active exploration). It helped my little ones to move from place to place - i.e We read the Bible story cuddled on the couch, did the Bible Activity at the kitchen table, the Fingerplay in the living room along with the Letter Activity, marched around the kitchen for the Music, and did the Rotating box at the kitchen table. One other little tip is to just stick to the HOD plans and keep them moving - don't expect "mastery" for things.
Each thing is meant to be done once, not over and over (maybe I'm the only one that needs to hear this
). I would not have the other dc do any of this - this is special time for just you and the LHTH duo.
After doing LHTH for a week, then I'd add in Beyond the next week. To organize different HOD programs, I just put the different programs in different plastic tubs. The LHTH child has 1 tub, but each other child has 2 tubs - one for the current books we are using each day, and one for the "books to come later". When we finish a book in the "current tub", I change it out with the next book we need from the "books to come later" tub. This makes it super easy for me to grab the right books, and it's easy for the kids too.
I'd keep LHTH first, having the older child and Beyond dc still doing their independent things. Then, you could have the older child play with the little ones once they finish LHTH - somewhere away from you, making sure they understand they may not interrupt you.
I'd start half-speed the first couple days. Here's an order we used for the left side boxes of the plans: Reading about History, Rotating box (geography, etc.), Music, Bible study, Poetry. For the next day, here's an order we used for the right side of the plans: Storytime, LA Spelling, Reading Choices, Math, LA copywork.
After doing LHTH and Beyond half-speed for 4 days, the next week I'd add CTC half-speed. This will have built some anticipation for CTC child!
I haven't taught CTC yet, but I think I'll follow a similar order as the other guides - doing the left side first, and then doing the right side of the plans next. Your CTC child could do the Bible Quiet Time first thing in the morning in his/her room (if an early riser
- if not an early riser, could do it later). Then during your LHTH teaching time, CTC child could do Reading about History box (since it is independent), and Beyond aged dc need to do something independent not interrupting you. If time, CTC child could begin the Independent History Box. Then, after LHTH is done. You'd be with Beyond dc and CTC child could play with LHTH children while you are teaching the left side of Beyond. Then, perhaps Beyond dc can play with LHTH children - or they can all watch an educational video together, while you do your teaching time for CTC. I'd start with Storytime, then Bible Study, chat about the History project to be sure he knows what to do. Then, perhaps LHTH children can have juice/snack/puzzles/coloring, etc. time while you finish Beyond's right side with those dc, and CTC child finishes history project and does Science independent box. At this point, your LHTH and Beyond dc would be done and can go play, do Books on Tape, etc. and you can rough out the rest of your CTC child's schedule, finishing with LA, math, and poetry.
These are by all means just ideas - I'm just thinking through what I'd do with those ages and programs, and I totally know that this is a plan that will need to be tweaked and modified to fit your day and your family. My best advice is still to start slowly and soon, beginning with LHTH, adding Beyond, and then adding CTC. I know it won't go perfectly (nothing ever does
), but I think you'd find your rhythm and settle into a good routine. Your day will be longer at first, but after a month in, you will be able to shave more and more time off as you all become more efficient at doing school (that's what we found when using multiple programs). HTH - I know you can do this, Liz, and I know you are going to have a fantastic year with HOD!
In Christ,
Julie
I have my 10 y.o. ds doing CTC. My 5 and 7 y.o. dd doing Beyond w/different levels of LA and Math. I have a soon to be 4 y.o. ds and 2 1/2 y.o. dd working on LHTH (the 5 y.o. will join in for parts b/c she enjoys it.) We may just do LHTH 2 days a weeks, as per Carrie's earlier suggestion. 
We are also going to do it 4 days per week as we have a homeschool coop that we do once a week. I am looking forward to hear the responses to your post!