Question: What would be the best way to get signal throughout a football field?

So I am trying to help a friend setup a small event on their football field.

On each corner of the football field there will be a computer. 4 computers in total. There will be sharing text files nothing heavy like music or videos.

What would be the best way to get all 4 computers to talk to each other without running soo many cables?

What would be the best equipment for the job?

My budget is about $300 to $600.

The signal doesn't need to reach the stands or the stadium. Just the center of the football field.

Any advice/ plans would wonderful.

Thank You for reading.