There are a lot of influences these days, in movies, cartoons, schoolyards. GI Joe, pokemon, UFC, etc.
Some of the most dramatic healings in all of my life have been the result of tending to children. I've experienced major healings at the heart level by trying to become a good servant to the child.
Play fighting is perfectly fine as long as the child is just exploring their body once and a while. You want to begin and end the session with you are being the dominant consciousness. The child's cosnciousness should follow your cue.
If the child doesn't listen, take away their privlidges and/or put them in time out, and end each exchange with hugs and kisses. Make them feel so good that time outs feel really bad. Hugs and kisses.