Have you ever dealt with 5 year olds? They're so small and fragile. I mean, dropping morals for a second and being theoretical, it's probably easy as hell to knock out a 5 year old. It's definitely also a crime to attempt this so you can't exactly test it, but considering its possible to kill an infant by merely shaking it, you'd think the threshold of physical ability to knock out a 5 year old would be relatively low. One blow to the head or one hard blow to the body. They're not going to take the pain and continue on, at least anywhere near full capacity. So even with a dozen of them attacking you at a time (and that's about all that could reach you at once even if you were surrounded by them in 3d) you're pretty much guaranteed to be able to take on 5 year olds not based on quantity but based on your stamina. If you got to a point where you could grab one and swing him/her around as a club, you'd be unstoppable.