How to help Android users with reduced ability to see What can we do in Android phone to help users whose ability to see is reduced?

To be clear they are not blind persons, they are just 55+ years old and with age they have reduced ability to see.

When my father has seen Xperia with 4.0 inch display he thought that his troubles with using the phone were over. Trouble came again when he realized that font size is still small because of large resolution.

Most of them are just simple users and they have needs only for seeing time, date, contacts, missed calls, incoming caller id, and dialer.  They're not even using SMS.  

What can I do to increase size of these functions on display, and make it simplified to access as it can be?  

Is there any app or theme or something similar already made for helping "older" people using phone?
You could try using LCD Density Changer to decrease the density (effectively increase the size of everything on-screen).  This will probably result in the bottom and right side of screens being cut off, however.

There are also (limited) accessibility options in Settings -> Accessibility.  I think it might be limited to a screen reader.

If the problem is really just things on-screen being too small, may I suggest eyeglasses?