Hi Shar-
This must be a tough time for you and your family.
I completely agree with Dave, that your idea of having a schedule for your mother each day is an excellent one. Routine is absolutely the most important thing for people with Alzheimer's. I would think that 4-5 hours a day would be enough stimulation for her, but I don't know if it will be enough of a break for your dad -- I guess all you can do is try it and see how it goes.
This sounds like it could be a real challenge for your father and you and, possibly, for your mother. How is she adjusting to being moved back home? If this gets to be too difficult for your father, are you and he open to her going back to the nursing facility (or a different one)? A lot of times, we think the Alzheimer's patient will be happier at home, but they actually may do better in a facility with structure and other people who are like them. It's just something to keep in mind if your father starts getting overwhelmed.
If you can, maybe it would be helpful to have someone come in for a couple of hours in the morning to help get her bathed, dressed and ready for the day. At some point, your father may find those things becoming too much to handle, so it might be good to get her used to having someone help her in the mornings.
There's so much trial and error in caring for someone with Alzheimer's, but it sounds like you have the right idea by giving your mother some structure and activities to keep her occupied.
Please stay in touch and let us know how she's doing.
Carol