Hmmm, 9 years old seems kind of young to be walking to and from school, and being unsupervised. My son started walking to the library after school when he was in 4th grade. He did this with other kids from his school (at that age, the kids didn't want to do the after school child care at the school). We lived in a small town where cars strictly observed the 'stop for pedestrian' laws (New Hampshire - very vigilant about this law). He had O&M instruction and the instructor took him through how to cross safely, and the best route to use to get to the library (no cutting through alley ways, etc.).
From what you describe, I do have some concerns. For example, the O&M instructor is just going to follow him? In my son's case, ours actually did instruction first, then walked him through the route, and finally watched him do it. The other question I would have is about the safety of ALL children who are waiting in that parking lot. Low vision is one thing, but being unsupervised at age 9 is quite another. Whether you have low vision or not, I would seriously question the advisability of allowing children at that age to be unsupervised anywhere. I guess that I would pursue that question - how is the school providing for the safety of all the children who wait in that parking lot? Is there an adult that ensures that the children get on the right bus? When my son was in elementary school, there were teachers specifically assigned to parking lot / bus duty and they kept an eye on all of the children (not just those with low vision). . .
The low vision and issues in albinism are quite unique, so I think your experience is probably similar to a lot of the parents here. I was fortunate that my son's TVI (for 8 years) had experience with several children with albinism, and was well aware of the specific vision issues associated with glare, and so on. Unfortunately, albinism is still pretty rare so even experienced TVIs (and even O&M instructors) may never have dealt with a child with this specific eye condition.