Welcome to the HOD Board - we are so glad you are here!

These ladies are so helpful, aren't they? I thank God for this board - such a wealth of wisdom shared in such an encouraging way.
I do think you have your dc properly placed in Beyond and Bigger Hearts.

As it is your first year homeschooling, do you think you would like to just try to do 1 program with the 2 of them though? They are actually quite close in age, only 2 years apart, and could probably work together if you upped the LA/math for the older. I think I have an idea to try. Could you start with Beyond Little Hearts for the 2 of them, and get the Bigger Hearts guide just to up the LA/math for your older dd? Then, a few weeks into the guide, I think you'll be able to tell if you should just move your older dd up to Bigger Hearts, and you'll already have that manual, the LA, and the math anyway, so you'd be able to probably better make that decision then.
If you did this, you'd probably have your 6.5 yo do the spelling and 1 x a week grammar from Beyond. You can choose between the Emerging Reader's Set or Drawn into the Heart of Reading Level 2/3 for your 6.5 yo. Though 2 of my dc were reading quite advanced levels of books when doing Beyond, I still had them do the Emerging Reader's Set. Even though it was easier reading for them, the comprehension questions, exposure to different genres, and beginning oral narration skills that were taught were a big help. The Emerging Reader's Set goes up to Level 4, so though it starts out easier, it clips along.
For your 8.5 yo, you'd have her use Bigger Hearts dictation for spelling and R & S English 2 for daily grammar (it is a year advanced), as well as Drawn into the Heart of Reading Level 2/3, choosing whichever DITHOR book packs you think fit her.
For math, you can give each of them the Singapore math placement test. It is free and can be printed right off their website at...
http://www.singaporemath.com
Be sure not to read the directions to them or help them during the test in any way as this inflates scores. Singapore math is considered a year advanced, so don't be surprised if they place a bit lower than you expected. Beyond has hands-on plans for 1A/1B, and Bigger Hearts has hands-on plans for 2A/2B, as well as a schedule for 3A/3B, so wherever they place, I think you'll be covered.
This is just an idea - if you are feeling you for sure want to do Beyond and Bigger then you definitely should! I am just thinking this may be worth a try. If you keep the 2 of them together this year, next year, when they moved on to Bigger Hearts, your older dd could do the extension package. There are extensions for Bigger Hearts on up in HOD, so you'd be set. Combining Ava and Anabelle would make it very doable to begin either Little Hands or Little Hearts for His Glory mid-year or so with little Charlotte. However, you will know best here though! Keep asking questions until you are set to go, we like to help here! We have loved HOD so much and have been doing it for 9 years. I pray it blesses your home as it has ours!
In Christ,
Julie