We use KJV. If your 12yo is having trouble with it READ LESS each time so you don’t feel pressured. Really. When we are having little ones or not so little ones who ask questions over every single verse we rejoice (!!!) and plan to only cover a few verses with them that day but answer all their questions or explain things. Isn’t that what we really want – children who learn to understand, not children who breeze through something easy and take no thought for what it means and how to apply it? Don’t get me wrong, I’m not saying that if they use a different version that is what they will do. Just saying that for any version what we really want is for it to challenge them to think a bit deeper and grab hold of the verses. So what if you can’t make it through a whole chapter each day or whatever you planned? Even one verse, when discussed, pondered, and applied, breathes life and the Spirit of God into your life.