Yeah, I mean I don't like just anyone ride the horses I work with, because it's so easy to mess them up!
But I think it will be great for Phantom to do some light work, both mentally and physically (if he's checked out first, and then every once in a while!) I'd say just keep an eye on him, but I think he'll be fine just walking/trotting for a while.
Every great dream begins with a dreamer. Always remember, you have within you the strength, the patience, and the passion to reach for the stars to change the world. ~Harriet Tubman