Broccoli is good as well, because it contains a lot of protein. The babies can still drink some milk, though mama, being an adult, is probably lactose-intolerant. A small amount of meat is fine, as long as it's not the majority of their diet. If you were going to keep them for any length of time, it would be good to give them Oxbow rat food, which can be found in most pet supply stores, as the bulk of their diet. (Harlan Teklad or Mazuri blocks would also be fine, but are hard to find in stores.) Good luck!