Well I’m sure you’re not terrible parents. I don’t have children but what I do know about all sleepers is that it’s about routine. Same things every night, in the same order. No screens or other stimulus 2 hours before bed. Exercise or any physical activity close to sleep too, but running around and playing football etc. before meal timed helps, and as for meal times light non carb based meals well before bed. Reading is a great way to unwind and helps the mind. Children have been less of a focus for me but before a neurologist I’d suggest a sleep specialist. They can come to your home and give you some tips. There are even ones focused for children. If you’re in the UK I can help with contacts. I hope that was in some way useful, as sleep experts have said to me regularly, it’s not rocket science it’s dicipline.