So, hypothetically, if you hit that child and caused serious injury, or worse death, would you be prosecuted?
Yes, you have killed a child. But it was 100% not your fault (assuming you were driving completely within the law, responsibly etc).
Unless you were speeding - no.
This unfortunately happened to one of my Wife's friends about 8 or 9 years ago (iirc), where a child of similar age bolted into the road from between parked cars.... sadly she had an Audi SUV and the child died as a result of the impact.
The mother said that the kid had managed to get free of her hand at the time, and sadly the worst outcome happened.
The friend of my Wife was investigated by the Police, and it took quite a few months, but she wasn't prosecuted or banned in any way. Though we never knew the exact details, as it was such a traumatic event - I would imagine that there were witnesses that confirmed she wasn't speeding, and the mother of the child confirmed that the child just ran into the road.
Such a horrific event - she didn't drive for about a year or so, as she couldn't face it, and to this day, has a handwritten letter from the mother that she cannot bear to open.
Not sure the law has changed since this event, but I expect if it can be proven that you weren't speeding, and couldn't have time to react, then you might only get a driving ban