iPad is definitely the way to go. We have my 81 year old grandma using one every day. She never really learned to use a "PC", but was able to pick the iPad up and use it immediately with very little help. Her first iPad ran for over 4 years before we finally got her a new one (to get a faster internet connection).

I also wish that you could pair up a bluetooth keyboard/mouse to different computers at the same time and just switch from a computer to another by a switch on the keyboard

This can be done in software using Synergy http://synergy2.sourceforge.net/. I have used it to share a mouse and keyboard between my Mac and PC for a few months now, and it seems to work rather well.