You’re thinking too small. You’ve got to ask to have your kids do everything you ask them to do.
So you say bedtime, they go to sleep. You say sit still and quiet for this particular moment, they listen. You say look here and smile, bam, instant beautiful family picture.
I’d settle for them listening after the third time I asked them to do something. I’m not greedy.
For the sleep thing, melatonin is magical. 1/4 of a 1mg melatonin chewable is barely anything but it’ll knock them out because they think it’s supposed to. I could switch to gummy bears now and I bet it would still work on them.