Plus, the fact that you said they refuse to stay in bed tells me that you are putting them to bed then going back into the game "to make sure they are in bed" which doesn't work. Once you put them to bed, you have to exit the game and then don't open it back up for at least 8 hours.

Even going into a different family to play messes this up. You literally have to exit the game and leave it alone for them to stay in bed. (I solved that problem by installing the game on a second user account on my computer.)