I'm getting to the end of configuring Grandma's iPad, but I'll call out one finding early.
For someone with low vision, Safari is the killer app. It has full screen reader support, and you can expand many (but not all) web pages with a pinch expand (spread apart).
This isn't true of all standalone apps. For example, the pretty but limited NYT Editors' Choice for iPad doesn't seem to work with the screen reader and you can't change the small font. The NYT web site though, is a pleasure to navigate using Safari.
Alas, not all web sites are Safari zoom friendly. The iPad optimized Gmail site can't be zoomed, so it ends up being relatively inaccessible.
As I configure her device I'm adding several web sites that are pinch-zoom friendly. Ironically, these have to be generic sites. iPad optimized sites are much less low vision friendly.