If your child is old enough to scream help then read this
Saturday night I had a Cub Scout Pack meeting and we had a gentleman come in from a company called "Kid Safe" and he taught the kids grip, dip, and spin.I can say from experiance as being the practice dummy.I swear to god my legs are killing me still.The things that was taught with this technique will drop any adult in a blink of an eye.
Grip - grab the kidnappers leg
Dip - fall to the kidnappers feet and wraps thier feet around kidnappers ankle
Spin - lean back or forward and spin the kidnappers knee ( Thats why Im so stinking sore)
Also when doing all this they need to scream for help.I had kids that weighed about 30 lbs dropping me like a bad habit, it really wouldnt have been so bad had they let go when they got me down.But instead they wanted to keep me down and twist my knee, in all it was worth it the experiance.