Your beautiful, trusting dogs represent a substantial investment financially and as a matter of heart. You don’t want to allow your pups to grow up fearful of strangers, and you need them to learn who to accept and under what circumstances.
This discernment is learned over time and with proper management, including limiting the opportunity for your dogs to interact with strangers in your absence.
My advice is to put up electric fencing and use signage. I would use a top wire on the side of the dogs, extending six inches or so from the fence and another one along the side towards the road. This will make it much more unappealing for strangers to reach through to “pet the dogs”.
It is also true that a pup shocked as he reaches towards a stranger will learn to associate that pain with something; the trouble with this is that you can’t control the association. It may be to men with hats, children, blue cars, who knows? This is a situation best avoided; I’d like to shock the stranger first!
Often when the dogs are new on a property, and little and cute, cars will slow or even stop, to get a better look. This can teach the pups to be reactive. As they mature and learn broader discernment on their own these instances won’t trigger the same response in the dogs but when they are young this can be a big deal.
I’m an advocate for clear, serious signs, such as “Guard Dogs at Work – Do Not Slow Down Or Stop! DANGER!”. Put locks on your gates when you aren’t home. This sort of thing may not always be necessary. Your neighbors will get over the newness and the dogs will become wise, if well managed. Don’t EVER let someone reach through the fence from the road side – no positive associations should ever come from that side of the world.