From the sidelines, it is tough to shoot from behind the LOS and get pass receivers looking back to make the catch unless it is a route across the middle. Short routes to the far side will have too many players in between you and the play to get a clean shot. Routes to the near side will often be too close to the sideline to give you a clean view without someone getting in the way (coaches, refs, players, etc.).
The easiest place to shoot passing plays is from behind the end zone when the team with possession is behind the 50 if you are using the 400. Once the ball passes the 50, I find it better to be in the other end zone or on the side lines at about the 10 shooting the play (of any type) coming to you.
Otherwise, from behind the LOS you can shoot the QB/RB handoffs, the QB throwing, the defensive players coming in, and sometimes a good shot of a sack.
If you'll have 2 bodies, put the 400 on one and the 70-200 on the other. Leave the 50 and 16-35 at home. Maybe take the 24-70 if there is some value to the on the field crowd shots post game and if you can get close.
Also, learn the team's play tendencies as it will help you set up for a shot. You'll find it difficult to switch cameras mid play as you see it's a pass or a run.