I say this from a kind place.
This is an issue that will keep coming up again and again for you and DS. we rarely encounter them impressive but unless you live on Lundy it's not sustainable.
Dogs are expect reading behaviour, from the moment they are born they enter human world.
Because you were bitten as a child you have natural body language which tells every K9 that sets eyes on you that they need to pay extra special attention to you over and above anyone, basically you have a great big sign over your head saying Unpredictable amateur
and because you in turn are not an idiot, you are aware dogs are a possible hazard, your son has learnt from you however unintentionally.
This creates a vicious circle,
You need to find a trainer near you who does a desenctising program(usually free), when we do it (super poplar as we have a lot of new comers to rural area, who haven't released how life limiting being dog phobic was going to be)
We teach individuals to read dog language, and communicate with dogs using body language.
If I walk into a space with strange over excited/aggressive dogs they will go quite and submissive. Even the most laid back well trained dog has no choice but to totally focus on you.
It can be easily changed and you/DS will be in control of any dog near you.
A good trainer will be able to teach you very quickly,
I suggest you have a quite chat away from little ears with the mum, and explain that neither yourself or DS is dog literate yet(no shame, it's just another language), and could she show DS how to be around the dog, ask her to monitor it.
We have very simple rules when children who are not use to dogs come here that maybe you could talk to DS about, as my dogs are working dogs they are perfectly behaved, so it is easier
If a dog is in it's bed you don't touch it, talk to it, look at it. This because all dogs need a place to be undisturbed, they cannot tell you they have a headache.
Never pet a dog unless it's bums on the ground. This tells the dog if you are passive you get attention, everything else I ignore you.
Only touch a dog if you have asked the owner and then ask the dog, if it's tail is between it's legs the answers no.
I really hope you find someone to take you through this simple process and this obstacle is removed from life. We have had a 100% success rate, it really changes things for people. Most people go on to get a dog because they become very accomplitish dog trainers, as the process requires an actual understanding of dog psychology, a near by rescue centre has a core group all of which ended up there because they wanted to implement their new dog control skills.
You are not alone lots of people go through this and never do anything about it, it worth addressing to get rid of the unexpected anxiety around every corner, and because it can make you a target for a dangerous dog.