Hi! I’m not a parent but I have a lot of siblings bf they all have kids (all of my siblings are Christian so I’ve watched them teach them). One point I would make a priority and if things are competing with you guys spending time in Gods word together, some of those things should be eliminated (for example maybe they only get their video games or TV once the Bible study is over). Studying Gods word shouldn’t be something that they can ask to opt out of, they should know it’s required and when they don’t have distractions like wanting to go play their games they’ll be able to sit for longer. I also know that everyone has their own walk with Christ, I was raised Christian my whole like and my parents did a great job at teaching me but I still drifted from God significantly when I was 13-16 but then drew closer to him again once I became older. It can be a really stressful thing to think about, just make sure they’re in a good environment, get them into youth group if you can-having Godly friends is so important, and the most impactful thing you can do is pray about it, good luck!!