A really lovely photo,Tim.
See how the suggestions by Des go but it's such a lovely shot of the pony that I think it would benefit by cropping down the sky which would focus the eye more on the pony. My eye was ,naturally, being drawn to that very light sky. My suggestion is to crop down to just above that small brown cloud above the large one, right side. You get to keep the distant hill and fog/mist which is integral. I did it with a piece of card and ,to me, was better for it. You could try it and 'undo' if you prefer it as it was or maybe compromise and include a little more sky than my 'crop'. It would also address the highlights issue raised by Des.
It's such an endearing, special photo I think you should have a quality print made and frame it.