Well, trail riding might do him good - just don't overdo it and go only as far and difficult as he feels comfortable with. Trails really help with tripping issues, becaus e they learn to be more careful and think about the road themselves. My guy used to act as a complete daydreamer, not paying attention on the terrain at all, and thus he used to trip a LOT, but much of his progress was made exactly in trails, when I just explained to him he had to be attentive and then the whole thing was his responsibility. He learned quickly that he cannot daydream anymore, as he could in the arena where I tried to do everything in his place and babied with him because of tripping. Instead of that, new responsibilities helped him to gain confidence, skills and balance.
I have come a long way, to surrender my shadow to the shadow of my horse.