Advice needed

Hi everyone I recently bought a property that was used to keep horses- approximately 9 of them. It seems that no one ever picked up after them- the stable doesn’t look like it had been mucked out in a very long time. There are two large fields that are absolutely COVERED in poop. Now I don’t imagine that they were meant to go around the fields and clean up- or maybe they were. I have no idea.

Looking for advice on what I should do. Is it save to just leave it - we have a 3 year old who would be playing.

There is one area in particular around a tree they were tied to where you cannot even see the ground.

Any advice appreciated!