Ask HN: Best computer set up for quadriplegic?

Hi HN, long-time reader with a question that I feel would be done justice by this community. My Dad's computer is dying and he's a quadriplegic with limited movement in his arms. (he can feel up to his forearms but can't move his fingers).

To date, he uses a refurbished Windows 7 computer with a trackball mouse and a pointer attached to a splint to type. He runs his own business online (something he did before his accident) and does very well. He develops his website on Microsoft Front Page. The man is dedicated and needs hardware to help him maximize his productivity and efficiency and the constant pecking at the keyboard isn't ideal for him and sometimes causes him to lose heart and try again later. I don't want to work the man to death but he's only happy when he's working.

He also has an old Android tablet he likes to use to browse the internet at home and check his email.

I'm recommending a MS Surface for him and I'm wondering if there's anything I need to know from an accessibility standpoint. Are there better options or tools out there for him? Happy to answer any questions you guys might have.

Thanks!