A litter of kittens would be a difficult meal for a rat snake. A snake can eat a meal that is 1 to 1.5 times it's body diameter. That's it. Maybe kittens a few days old might be at risk but not likely. The snake in those pics is a sub adult. The reason you can tell is that you can see the markings on it's back. As black rat snakes age, those markings will disappear until the snake is almost perfectly black with a white belly. At most, it's 3 to 4 feet long. It will eat mice, young rats, young birds, etc. It's not going to be doing much of anything to children, cats or dogs.
There is a lot of misinformation out there about snakes. A lot of people are terrified of snakes and there really isn't a reason to be. A black rat snake is a very good animal to have around. They do more to protect you than you'll ever realize.
And yes, I know about snakes. We keep about 30 snakes as pets and I am able to interact with several snakes that reside around our house including garter snakes, black rat snakes, ring neck snakes and others.
Here's a pic of my daughter with one of her pet snakes...
