Warmth is going to be so critical. Too little, too much - same outcome. I'm thinking a mama mouse's temp might be around 104F (at least). Maybe a chick heat lamp with the pups under a light cotton cloth...I know they are not capable of any temp regulation until they have some fur. The other problem we had when my daughter tried to save baby rats after the dogs destroyed the nest (yea, I know) was that they aspirate very very easily. I think the ones we tried to save died fo pneumonia. Good luck.
Another idea...Any wildlife rehab place you can call? Wouldn't be too much different than a chipmunk?