PaulJenny,
To be completely honest with you I wouldn’t tell the employees about his CAH. You don’t even have to mention that you take care of children. These are all questions that are completely illegal to ask in an interview. Once CAH is controlled it’s normally very predictable. I would assume your grandson will grow up healthy. The only time this subject should be brought up at work is if you have been missing work because of him or because you need to make arrangements. Take the job and assume the best. You deserve it, it’s extremely honorable that you are raising your grandchildren.
Paul