Get one of those (I hate them, but they last a long time) Chinese low watt florescent light bulbs and put it near where the kittens sleep. Coyotes will stay away.
The problem is the cats don’t stick around at night. They wander around the farm, hunting. If they stayed close to the house, it wouldn’t be a problem.
So now we bring them inside at dusk, which is when the coyotes head out of their dens. There are a couple of packs in the area and our farm is part of their territory.