I don't know if this will help but this link from the NAMI (National Alliance on Mental Illness) shows how mental illness can be covered under the The American with Disabilities Act.

NAMI | The ADA – Americans with Disabilities Act

Does the restaurant employ more than 15 people? That seems to beg key to them having to comply with the ADA.

Not to load you down with more on your plate, but something to consider.

I hope that you are not anyone's joke. You are not one here.