My top advice would be to keep her off the road - all roads - for as long as humanly possible.
In my experience people cycle *despite* the numerous issues such as traffic safety (not because they have found a solution to them) and so you need to build up a strong foundation in "cycling is great" before you expose your wife to the inevitably dark reality of trying to get anywhere.
North Edinburgh path network, Innocent railway / park, the canal, Water of Leith, riding in the Pentlands (depending on your bikes, this is fine without having to own a MTB). All of these would be great venues once you've got the basics of riding the bike down to the point that you want more than just a car park, or the road outside your house (if quiet).
Oh, and in my opinion (controversy alert) if you're faced with a moral dilemma regarding giving up cycling or riding on the pavement, you should try to get comfortable with the idea of riding on the pavement until that hump is past. A lot of cyclists, many on CCE included, don't agree with this, but I think society as a whole benefits more from a bit of pavement riding leading to one less car. YMMV ;-)