All great advice.
Just would like to re-emphasize the TWH doesn't even need keg shoes for the trails.
When I was hard trail riding one of my horses wore rim shoes with borium head nails. His hooves were trimmed in a normal fashion that one would expect to see on any trail horse.
The other TWH has hooves like a goat and has been ridden barefoot in some pretty rough places much of his life. He even has a less-than-grade 1 club hoof but never sored up.
Also want to re-emphasize that it is not a good idea to shorten his toes/heels up too fast. That can lead not only to soring the hoof but soring the tendons.
Your friend still has all winter to get his "wiggies" trail ready; just do what's right and makes sense for this particular horse (meaning shod or barefoot)