Small dog + Big pups

We have a little Lakeland terrier, she unfortunately escaped whilst in season and got herself mated. By the time we realised (irresponsible and inexcusable I know) it was too late to abort and she had 2 large pups by caesarean section. A week later they are HUGE!
The poor little dog is exhausted, thin and perpetually hungry from feeding them.
Any advice as to diet, helpful articles to read plus things to avoid would be welcomed. Criticism and accusations of cruelty are superfluous, we are perfectly capable of that ourselves.