I agree that children should learn martial arts. I began training in martial arts, Tang Soo Do, at age 8. Now at 18, I truly see the benefits of the martial arts life style. I certainly intend to teach my future children martial arts as well.
I think the greatest gift of martial arts is learning how to not fight. In fact the main goal of martial arts training is to avoid fighting all together, but be prepared if necessary. Also, a student of martial arts stands to gain a great deal of confidence from his endeavours. I remember the sense of achievement I felt after breaking my first board and earning first place and my brown belt. Additionally, there are social benefits to martial arts training. Since martial arts are so mainstream now, the potential to make friends is quite high. Lastly, studying a martial art can be just like playing a sport, yet it has the potential to be an entire way of life. Early introduction to martial arts is the key to beginning long-term study.
In closing, teach your kids martial arts!