hmm... well, I know if it was me, I would never be able to leave my boys behind anywhere. But it is a complicated situation.

Just consider all of the possibilities. Would people renting the house appreciate the dogs roaming? What if they have dogs? Your girls are young now, will your Grandpa still live there and be healthy enough to take care of them in 10 years? What if one of your girls was hit by a car? It just doesn't sound safe.

In my experience, it is not hard for "outside" dogs to adjust to living indoors. Gonzo was an "outside" dog from birth in his former home... and he LOVES being an inside dog, now. It's just a matter of adjusting them slowly, giving them plenty of outside exercise, and teaching them inside manners.