The average 6 year old weighs less than 50 Ibs and is about 4 feet tall. As a man at 18 in relatively good shape and at a height of 6'0"" and 160 Ibs, these would both be advantageous enough to take on as many 6 year olds as necessary until I suffered exhaustion and passed out. I'll explain.

Assuming the 6 year olds are coming in a high frequency, but not packed back to back like a zombie swarm, I would start by kneeing the first several children in the heads. That force applied to the head of a child of 50 lbs would likely either break their spinal chord or at the very least knock them unconscious with a traumatic brain injury or brain bleed.