You might want to search for information on "marketing to
mature" consumers. There's quite a bit of data out there.
I've done work in this area, but it's been several years.
Here are some basics:
* Use a plain background.
* Use animation judiciously -- flashy stuff can be
distracting and overswhelming (our peripheral vision
changes as we age). Delivering text one line at a time
can be ok but use a simple "appear"
* Use a san-sarifed font (less stuff to look at).
* Make sure your text is a very high contrast against the
background.
* "Bold" accent colors are enjoyable. Avoid red/green
combinations (color blindness)
* Limit the amount of stuff on your slides (again, too
much stuff becomes overwhelming)
Sandy