Creating adaptive copies of textbooks using text-to-speech

My institution subscribes to the "Kurzweil Reading Program", a "Text-to-Speech" product for those with reading impairments (dyslexia, English language learners, blind/vision impaired, etc.)

Section 121 indicates these users are "eligible persons" for "fair use", but others, without such disabilities could use the program (like an audiobook in the car!).

We'd be putting TEXTBOOKS up in the program; that fair use violation is what I'm worried about....

Thanks!