My son is almost 10, and I'm in "no" mode right now. He has friends in others sports he plays that also played football, and a couple suffered concussions. You can only get ones bell rung so many times, and I want to limit that possibility.
I fully acknowledge and understand other sports and activities can lead to concussions. My guy occasionally plays goalie in soccer, and he plays baseball - sports where head contact is foreseeable. He also plays basketball, which seems less risky, but a couple kids collided in recess playing hoops and one got a...concussion! I'm more concerned about the repetitive contact that is guaranteed to happen in football, both in practice and games. Especially if one plays line. If I read up on this right, the younger kids are at risk as much from the brain rattling around in the skull, so helmet technology really can't do too much to reduce that. The idea that the brain still has to grow into the skull as they age.
He's been asking me to play lately. Some of the football coaches have coached him on other sports, may be trying to put some thoughts into his head. I played a little, 7-9th grade, and didn't play a lot and was more interested in basketball, so I quit. I'm sticking with no for the near future (he will be in fifth grade next year). I'll consider it once he hits high school. I'm not worried that he'll be behind in the sport - it's a risk I'm ok with. If he has skills to play at that age, the coaches likely will find a place for him to play. We have plenty of footballs at home and will throw it every once in awhile. And punt and kick.
I'm erring on side of caution. And frankly, I don't fully trust the coaches on our area at his age group to watch out for his well being.