Something we did at martial arts class that was safe. Basically you have two people in a ring. The “ref” says “go” and the two youths have to at least touch the other person on the knee to get a point before the other person. When the person’s knee is touched then the ref calls who got the point and seperates them(and don’t worry about being wrong. You called it, and it stands because you’re the ref:). Repeat the process.
If you’re having trouble visualizing this then watch a boxing match and then picture them slapping each other’s knees and you should get the idea.
The first person to 3 or 5 points wins. A lot of fun and safer than kicks to the head.