My son just loves football.  He plays for his high school team. Football ranks among the most popular sports
My oldest son has also played football for an elementary team. How have you managed to keep him motivated to play?
He needs no motivation. He loves football and watches it all the time. He is forever telling me the rules - about the offense and attempts to advance down the field!! 
That is great. He must be exciting to watch and fun to be around. I hope he continues his passion for it.
fingers crossed.  It is good exercise and they learn great teamwork with the scrimmage, passes and techniques.