We had a fantastic holiday, in no small part due to your planning! The walk was excellent - truly excellent - and skiing and Tokyo were both also really enjoyable. We had perfect weather - plenty of snow and sunny days for skiing, just enough snow to make the walk beautiful but not so cold as to be arduous.
It was a wonderful trip. We had very few navigation issues. Even though my Japanese is lousy, it was very helpful and I think it would be quite difficult for a group without any Japanese (especially reading).
We have recommended the walk to everyone - most would need pretty strong guidance so I think your business will do well.