Today while I was sleeping my sister came over and mowed the lawn. That involved getting the mower from the shed, thus disturbing the feral cats. She also put food and water near the shed door, which I'm sure the mom cat wouldn't like. Food and water would be bound to attract other beasts right to her kittens. After I woke up I saw the mom cat int he back yard, and the gray cat was out there too. The mom cat left the yard, going off toward the woody area northeast of the house. The gray cat stayed behind. I don't think she'd have left the kittens alone with the gray cat here. My guess is the day's changes were too much for her and she's moved the kittens.
Later I went out to remove the food and water bowls from near the shed, and I looked in and saw no sign of the kittens. There are a couple of places in there they could have been hiding, but I didn't inspect too closely. Just in case they were still there, I didn't want to chance giving them yet another fright. But I'm pretty sure they're gone. Maybe now that the food and water have been removed the mom cat will bring them back, but probably not. This place probably doesn't feel safe to her anymore.
But the lawn has been mowed.
I don't like what I have to fix for dinner. I'd better get it over with.