Let them play for a while. Pick a point in the game when everyone is clustered around one goal and freeze them. Ask them to take a look at the open goal and ask them which goal would be easier to score on - the one they are currently trying to blast through or the open one on the other side of the field. They will usually see the light. Let them play some more.
Conclusion Have the kids pick up all of the cones.
Review the focus of the practice very quickly, do your team cheer and send them home. After doing our team cheer, I have the girls run to their parents doing the airplane and yelling Gooooooooooal and give them a hug and thanks for bringing them to soccer practice. I was rewarded in the scrimmage at the end of this practice when one of the girls paused while dribbling, looked up, glanced at both goals, saw that one goal was covered and the other was open, dribbled like crazy to the open goal and scored. I just happened to be in a position that I was able to see her face and eyes when this happened. The excitement I saw on this 6 year old's face when she noticed the open goal was a picture I will remember for a long time.