I don't have sons, but, if I did, I certainly wouldn't encourage them...
to play organized tackle football (I wouldn't ban it outright, either, though). After reading a couple recent studies regarding head injuries and football, there's just no way push any child of mine out on to the gridiron. My brother has seizures to this day (he's in his early 40's) as a result of a head injury he sustained playing football as a teenager.