After the family had moved into the Old House after having been driven out of Collinwood by Quentin's ghost, we saw (in Ep #695) the room that David was sleeping in:
(I don't even want to speculate about what that is on the table.
)
So, we definitely know that at least one bedroom other than Josette's had been restored at some point. Though, with the whole family staying at the Old House, I would presume we can believe other bedrooms were also restored. However, the idea that the others slept on cots in dilapidated rooms is quite funny to picture.
I can just imagine what Roger would have had to say about that!