My general dog rules for children...
No running or sudden loud noises when approaching a dog.
No hugging.
No pulling of anything.
No giving (sharing or general waving) of food. (Unless it's dog treats with the owner's permission)
No playing with dog toys unless the owner says it's ok.
Dogs lying out of the way, in bed or otherwise should be left alone.
Dogs prefer to be approached sideways and to sniff a hand before it touches them...and the head is not always the best place to stroke, the back of the neck or back is better.
A dog looking at you with it's eyes showing the white and licking it's own lips is asking you to go away.
A dog on its back doesn't always want a tummy rub - with some dogs it's asking you to leave it alone, always check with the owner.
Other than that, I wouldn't worry at all about breed and I've had large dogs in flats, unless it's a tiny space it makes no difference to anything. Gardens are handy for housetraining, but walking is where they get exercise.