Yes giardia can sometimes be passed from a dog to a human.
However the good news is that the risk of getting giardia from a dog is very small so I wouldn't worry too much about it.
To be able to get giardia from a dog or other animal you would have to swallow the parasite that causes giardia which most adults would not do because you'd basically have to eat the dog poop to swallow the parasite where it resides.
Now if you happen to clean up the dogs poop with your bare hands and then do not wash your hands then it could happen but you likely would use gloves or a shovel and even if you use gloves to pick up dogs poop then you should wash your hands anyway.
Never allow a child to touch dogs poop or swallow it because it can be harmful to your child.