What should I do about this?

I've just put my 19 month old in his own room and his new "big boy" bed. That alone is enough for him, but on top of it my landlords granddaughter and her boyfriend have just moved into the downstairs apartment (it's a duplex so it's just the us on top and them downstairs) and they put up a dogpin right outside with three bulldogs. They are litterally right outside my little boys window. I had a really hard time getting him to sleep tonight because they kept scaring him, and now that he's finally asleep, they won't shut up! My landlord is really old, so I don't want to call him at 10:30 at night, and I don't want to go down there causing trouble, but this is really pissing me off. If they wake him up and scare him I'm going off! What would you do?