Daughter or son, I too would be very hesitant about letting my kids play a sport that is basically all about getting hit in the head.
I'm all about getting my kids involved in sports, and think (certain) martial arts can have great benefits. Confidence, the ability to defend themselves, the self-control they need to develop to follow the rules /code of honour. Judo, karate, jiu-jitsu, absolutely. Boxing, no.