Take the dog to a vet and get it euthanised. Don't speak crap about not being able to afford it. Find the money and you or your kids go without something for a week, do whatever it is not very espensive. Our dog was actually free to put down (at 15 yrs old) because we have a kind hearted vet. Anyhow regardless of the cost you got the dog, so you now need to deal with the issue in a humane way.