I recently went through this for my 91 year old father-in-law.
Please read https://developer.apple.com/technologies/ios/accessibility.html
First, your Mom's ipad will have VoiceOver (all ipad versions do.)
She will need a wireless router to use ipad at home. These can be rented via cable providres, though most people buy a router and set it up themselves. She will need an internet connection at home, and many elderly people, like my Mom, have no interest. If or once she is set up
Go to settings. On the right side of the screen, scroll down to the very bottom, (it does not show until you scroll all the way down) > accessibiliy> that will take you to another screen. On the right top, slide VoiceOver ON. When your mom puts her fingers on an app, it will tell her what the app is. If it's not want she wants she can tap others until she gets to the ibooks app. All her books can be stored in there.
Please be aware that once VoiceOver is on, scrolling and different tapping will come into play.
There are some videos on youtube, specifically regarding Voiceover for the vision challenged. There are many apps that can help your mom with brain games that you might add in as she gets more comfortable with the ipad.
Regarding apps on opening screen, please read http://ipad.about.com/od/ipad_tips/a/Great-iPad-Tips-Every-Owner-Should-Know.htm. You can create a folder, drag and drop what your Mom will not need, and move it down to the tray at he bottom of the screen.
Also, though I havenn't found a way to make the apps you'll kep on the opening page larger, your Mom can, with VoiceOver, be told what she dealing with.
You and she can use FaceTime to talk and you can do this without a cellular ipad. It's built into all ipads.
http://www.apple.com/ios/facetime/
When I think of other info that will help your mom, I'll get back here. I think ipads for seniors are great, and the more you read about how many things she can do with it, it can be a close contact for her to not only read books, but listen to music, play brain games, and use FaceTime to keep in contact.
Hope this helps.