I personally have the Handspring Visor Neo (monochrome, expansion slot). I would rec. a full feature model for your wife, but it sounds like you would be better served with multiple units (phone, palm, GPS....)rather than expect the palm to do it all. You will find that all of those add-ons do not perform as well as any of the stand alone units. I have heard the GPS is WAY to fragile (friends went that route, and regretted it) and you are better off just buying a good handheld GPS, more rugged, easier to use, etc. For the camera, depends what you want it to do. Digital cameras are getting really cheap, I am not sure I would waste the effort tinkering with the palm add-ons.
For web surfing, I think the Handspring modem is designed just for a phone cord, but I could be wrong on that....