My son and neighbor's dog?

I've recently moved into a new duplex with two friends. My 18-month-old son will be coming there on a regular basis to visit me. I've recently found out that our land lady, with whom we share the garden, has a dog (border collie/lab mix) that seems to be very poorly socialised. Whenever we've been at her place to sign contracts and the like, the dog has seemed extremely afraid and has been barking like mad. Our land lady says that it's because he is a guard dog and that it takes him time to get used to strangers... I don't buy it. Even the most alert guard dog would not act this way around strangers if it was well-socialised.

The dog is often outside in the garden without a leash, and when he is not in defence-mode he seems like a wonderful, energetic and playful dog. Because I will be living here for years, I want to introduce my son to this pooch, but I also want my son to have good experiences with dogs just like I have had, and I am afraid that if the dog barks aggressively at him, it could potentially install a life-long fear of dogs in him, which would be a nightmare, as I am very fond of dogs and want to introduce one into the family in a few years.

So what to do? As I see it I have three options, but all suggestions are welcome:

1) Should I kindly ask my land-lady to only let her dog out into the garden at designated times, so that my son and the dog will never have to meet?

2) Should I try to encourage her to spend more time socialising her dog to people and other dogs, so that in time the dog will be happy to meet and greet my son?

3) Should I offer her to spend some time with her dog and provide some much needed training and socialisation myself before introducing it to my son?

Many thanks in advance.