keeping free range hens in

Better to lock them in than risk them to a fox, assuming they will get enough daylight during the day to allow normal feeding and preening behaviour.

If you give them some stuff to amuse them like a cabbage hung up to peck at and a cat litter tray full of fine soil or sand to dust bathe in, I'm sure they will be fine.  Chickens are accepting little critters and although they may create a racket at first, they'll settle soon enough.  Leave several water sources in case they turn a drinker over