There are some computers made for the elderly with special operating systems, but not as much for tablets yet:
http://www.mywowcomputer.com/
Here is an Italian company with Android tablet software (and computer software) for the elderly:
http://www.eldy.org
Here is another tablet directed to seniors:
http://memotouch.com/
Other software for PCs for seniors
http://www.softarama.com/Products/Seniorama/
http://pointerware.com/c/pages/home