My opinion..
Good with young children
I don’t think there is such a thing as dogs are so individual and it’s largely dependant on training/experiences as well as genetics but I’d generally avoid dog breeds with a tendency to be high strung/noise and/or movement reactive like herding breeds for example and I’d maybe avoid breeds with a reputation for being ‘no nonsense’ like terriers.
Doesn’t shed too much
I imagine you’ll be looking for a single coated breed then, or one of the ‘wool’ type breeds like poodles or bichons.
Not too energetic, can be content with an hour walk a day (we had a boxer who was very, very high energy and would like a more subdued character!)
I personally think this is less down to breed and more a combination of parent temperament and training.
I have a working bred collie.
Her mum was placid and lazy and my collie also is placid and lazy (though both dogs are more than capable of going all day if required)
Protective instincts but not aggressive (We live rurally and I’d like teen dd to be able to walk alone with the dog without worrying about her or anyone else)
I think you have to very cautious about this.
Without specialist training the vast, vast majority of dogs, imo, will not defend you.
They will flee.
And in order for specialist training to be effective the dog has to have inherited the correct temperament/balance of drives.
The majority of dogs bred for the pet market, of all breeds, do not have the correct temperament for protection work and cannot be trained for it either, they don’t have the right temperament, they are too soft.
Dogs that have inherited the correct balance of drives/protective instincts don’t always make easy to handle pets.
The only breeds that I personally think naturally still have some protective ability left are the (good) working lines of German/Belgian/Dutch Shepherds and the livestock guardian breeds.
But I’d hesitate to recommend them.