I wrote further up the thread of the loving and clean chaos that operates in DS's home. As said the children are loved and cherished and the parents, after over 20 years of marrieage are as close as ever.
For the last week they have been staying with us, and all I would say to the Op, is just wait. All it takes is time. My eldest GD is 16. She can cook, she can sew, and she is highly organised and dreams of having a home of her own that would be beautifully tidy.
As it is she is quietly taking over. Not in any worried or concerned way. One day her parents will wake to find her organising them and their lives and keeping them all neat and tidy. It is a joy to watch!