I wouldn't be confrontational at first. Just bring it up in conversation. Of course that's assuming you know your neighbors and have conversations with them. If you don't, bring them a plate of cookies and introduce yourself.
Mention the dog situation and ask if there is any way you can help. Comes across in a more positive tone. Make sure to mention that no one is sleeping at your house. Make sure they feel the responsibility.

Now if nice doesn't work, I would then escalate it a bit. Also, buy earplugs.