They will attack and can cause great damage to a dog even if they can't get them off the ground. If they can fly off with their prey they will disable it with their talons and beak and just consume it where they have it.
When my Cali was attacked (and we were sooooooo lucky) even though she miraculously survived we still had to do the antibiotic shots and pills, and stitches, because hawks are filthy what the road kill, rats and such they eat.
Also, they are fast so don't be naive about that. Stay close to your babies!
Plus, you cannot kill a hawk. -- the fine is very expensive because the are protected by an international migration law.