I can't really say much more than what has already been said by others but I suppose I'll give my advice anyways.
Carry something blunt yet compact, I would probably take a Nightstick of sufficient thickness, hollow it out, and weight it with some lead. Probably not practical for your wife but I'm sure you could de-brain a dog with it just as well as I could.
I would get some bear pepper spray, never used it personally, but from what I've heard it is potent stuff. I'm betting it runs out real quick though so I would use regular pepper spray first, and save the bear spray in case it fails to work or runs out.
http://www.udap.com/ <- A company that sells some, just looked it up as an example.
I'd wear a baggy coat so I could unzip it and use it to increase my profile. If I'm right, it would make you look much larger then normal to the dog. Combine that with a cautious retreat and it could save you from some pain.
Getting a buddy to walk with would be something I would try, having your buddy equiped with the above would make you both quite safe.
Acting confident while still being non-aggressive and avoidant would probably help a bit. You wouldn't be acting like prey and hopefully they wouldn't consider you as much a threat to their territory due to your aloof and passive nature. Keep in mind that from the dogs perspective your an invader in "their territory", this probably lowers the usual effectiveness on non lethal deterents. So I would say prevention would be the best solution if at all possible. Though from what you said it isn't really a choice.
Thats about all the useful advice I can think off atm, I agree with most the other suggestions in the thread also. Especially the spiked leather idea.
As for what I would
REALLY do in your situation though, I would kill the dogs despite the law. Especially when loved ones are at risk...