Bob, if your laptop is anything like mine, you will prefer the display on the GPS. They make units with relatively large displays for reasonable prices these days. My Garmin Nuvi has a 4.3" screen and is very easy to read. Unless your wife has vision problems that require a large laptop screen, I'd suggest a standard 4.3" screen.
The GPS screens are made to be easy to view in direct sunlight, much better than any of my laptops and the touch screen functions are very easy to operate, versus a laptop which requires key strokes, etc. My GPS is a couple years old and a basic model, but I had a chance to play with a friend's new, fancier model. His had real-time traffic, and voice activation, etc. It gives you an alternate route and lets you plug in an address without punching keys. Much nicer and a much better screen than my 2 year old unit. The new GPS's are really cool and very inexpensive.
You'll need to do research to see what works best for you but I was impressed with the model that had voice activation and real-time traffice.
