I'll recommend a Nuvi 255 or 255W (widescreen). The 255w currently on sale on amazon (cheaper than the regular 255) and it's simple to use and it speaks the streets name when navigating you. My parents were really stubborn with the idea of trusting technology to navigate them at first... the Nuvi 255 I got for them changed their mind quickly and they have since become addicted. It's very parent friendly, no real skills required.
The 255 isn't packed with features... but it does what it's intended to very well - navigate you to a destination while speaking directions and street names.
If you are interested in getting something fancier, you can get ones with bluetooth, music playing ability and all sorts of awesome features.