I expect I would:

Try and hit the first one that got to me, but probably not quite catch it right.

I'd shriek 'Ow, fuck me, that hurt' and start waving my hand around trying to soothe it.

In the meantime, they'd have taken me down from behind, after which I wouldn't stand a chance.

So in answer to the question:

Method: Weak punch to the head, resulting in me coming off worse than the 6 year old
Number dead: 0


Seriously though, have you ever seen a 6 year old in a bad mood? That's nothing to be sniffed at.