That, and/or possibly killing several other people. I'm not advocating that people run over the kid at all, I just mean: always be aware of people behind you when braking quickly.
I don't know about other people but as a driver I try to be aware of what's behind me at all times. Where I live (Sydney Australia) it's extremely rare to be tailgated on a suburban street — but when I am, I'll drive to the conditions. That means in an area where road incursions are probable (e.g. where there are pedestrians or playgrounds) I will drop my speed below the limit. If someone is being persistent or aggressive, I'll pull over and let them pass.
The drivers behind you are responsible for maintaining a safe following distance so that you can slam on the brakes when a kid runs into the street. It’s not your job to worry about them. Eyes on the road in front of you.
You should worry about what's in front of your car first and what is behind it after. There's a reason we ~always assign blame to the car that does the rear ending.
Don't tailgate, people. You never know when the car in front of you is going to slam on the brakes because a ball, small child, or plastic bag jumps out in front of it.
Kid has a t-shirt.