Day Games: In one sense day games are easier to shoot. There is a lot more light which means you can use higher shutter speeds to "freeze" motion and still use a fairly low ISO setting. A low ISO setting means you can avoid noise in your photo that ends up looking like "grain" from high speed film. You can use almost any lens in the day. I like a fairly long focal length so you can keep the point of action (the ball) at a large enough size on the frame to recognize what is going on. I have used a prime lens and the size of the action varies as the ball moves up and down the field.
Night Games: The park where the soccer is played in Mesa, AZ has nice lighting. Here I do use a 85mm f/1.8 lens because of its light gathering power. In order to come close to freezing action at night, I have had to adjust the ISO up into the noisy range. I found that setting ISO at 3200 or 5000 will give me a shutter speed of 160th to 200th of a second. Those shutter speeds freeze most action but sometimes feet or hands will exhibit motion blur.
The Players: Sophia is 5 years old. She aggressively follows the ball and dukes it out with the other team to take possession. Brayden is 6 years old. He is very athletic and enjoys running up and down the field.
One other thing: Crop your photos. Sometimes the action gets lost in the clutter of the full frame. Crop the full frame to isolate the action.
