Tablets need the fingers to do the walking.

The most important thing to understand about a tablet is that it needs good manual dexterity to be used. Also, setting at a desk working on a fixed screen can be easier (less frustrating) than having to hold the tablet and simultaneously navigate using the screen.

Also, keep in mind that a keyboard and mouse are still the easiest way of interfacing with a computer.

Personally, I would say no to the tablet question unless all your father is doing is surfing the web and doing lite reading of news/articles.

I have considered an eReader recently because I enjoy reading books but in this area my personal preference would be the Kindle. I don't necessarily need color and for pure reading I don't like the compromise you get when looking at tet characters on a PC. One of the models using e-Ink is my preference because the quality of the "page" is very close to a printed page. I'm trying to decide between the Kindle Keyboard and the Kindle DX.