How to setup an Android tablet for use by an older person
You would probably wanna:

-Setup a launcher like Nova Launcher (my personal favorite) solely to setup gestures for daily used tasks like calling and viewing SMSs.

-With Nova launcher change the icon size to maximum (130% i guess) to make icons more visible.

-Go to Accessibility and change the text size. Since it varies from manufacturer to manufacturer, the customizability may be different. Tinker around in the accessibility settings to find something useful. 

-Change ringtone, notification sound and alarm to something loud and distinct.

-Turn on Haptic FeedBack in Sound settings (varies from manufacturer to manufacturer again)

-De-clutter the home screen! May even want to sort them by folders (drag an app over the other)