testing out my new A7 III I used a 24 -105L for volleyball. It did really well. Of course I was courtside, so not an apples to apples comparison. But the take away was that the lens absolutely focused fast enough, even though I was using it adapted to a Sony.
So if you have field side access, I think you could early cover 20 yards either direction of where you are standing, and to mid field shooting across side line to side line. Pretty everything else would be too far away. But absolutely you should be able to get plays that come towards your, runs to your side of the field. My last kids team in pee-wee loved to run a wedge run. Those could be a challenge. But strong side or weak side runs or passes towards you... if you get low enough should work just fine.
The thing for football ( or any field sport) is no lens is going to cover a field. Just not realistic. So you either shoot shorter lenses and do a lot of walking, or have long glass and keep retreating as the play comes toward you. 24-105 would be great under the goal post shooting end zone action. I also found that as you zoomed it held focus really well. I was easily able to track and maintain focus from center bump, to cross court bump, and finally near court slam. (70mm-105mm-24mm).
Give it a try..... be creative.
