My wife's Mom has the same issue on her 20 inch iMac....the best accommodation that we were able to come up with was to use the Zoom function in the Accessibility PrefPane.
Helping her to understand that making everything bigger on HER screen did NOTHING for increasing the size of the fonts that are sent out by e-mail was a totally different issue. ;=))
We tried using the preferences within each individual program (i.e., Safari, Mail, etc), but that very quickly entered the "too hard" category.
The keyboard shortcuts for Zoom are pretty simple, but not everyone deals well with keyboard shortcuts.....
Option - Command 8 will toggle the Zoom function On and Off
Option - Command = (same keycap as the + symbol) will Zoom In {larger sizes}
Option - Command - will Zoom Out {smaller sizes}
Good luck with this!
