I've had seven families running at various times, from build 01 through every update to the current 05 and never had a peep REFUSE to nap or go to bed! They always nap on their own, and with praise, nap more often.

Sure, some of them nap less frequently & night times appear to be more troublesome, but they have never refused over & over if I kept trying, and most times it was one attempt and they went to bed, albeit not for long enough to regain enough energy. But you persist or just exit their night time and they sort it out themselves. It's not that bad if they wake up tired anyway, they regain a lot from naps.

I find playing their day time much more enjoyable, and if you want to check in at night, then exit the game for a while and they seem to recover themselves.