Hi
this sounds like trauma naggression to me. It is caused when something frightyenes the cat and they react by acting aggressivily. When the kids fell over i expect they cried loudly and this could have been the trigger.
The only way the cat will stop displaying this kind of behavior is by feeling secure again in the home environment and around the people who were present at the time of the trauma. It can be slow process of making a fuss of the cat in a calm quiet environement and to try and make the children act calmly and quietly when the cat is around as he is obviously stressed out by noise and stress. Difficult i know but it is probably the only solution. If the behavior doesn't subside you may have to comsult a vet about some calming medication.
Hopefully your cat will calm down and return to his normal self soon. :)
