C Ann--
First, I think that it is great that you have such a great relationship with dd and her family. It is good to see your responses to the questions. While yours are positive, unfortunately, in other relationships, they might not be. That is why they are questions that need to be seriously discussed between op and her dh and then with her mil.
My reason for not having my mom move in with us again is not because of problems it caused as we have had very few. It has to do more with the fact that she grew up in rural Iowa, town under 200, knew everyone, had her coffee klatches, afternoon tea get togethers, church activities, clubs,etc, was still driving when she moved in. She moved to our home, 300 miles away, metro Kansas City and could no longer drive due to traffic, no taxi service in our suburb at the time and no bus service. No relatives around. Very few people her age in our church and no activities for them. Dh and I worked so could not get her to senior activities here in town. Our neighborhood is a young/middle aged neighborhood, so noone to converse with or share coffee with.
My mom (who is 88 now) goes with us to neighbors houses--we have super neighbors who adore her-- and went to most of our ds's activities and to visit our dd and family until it was just too hard for her. She and ds have a super relationship. She loves to see his friends and they are very respectful towards her and take the time to converse with her. The noise they make doesn't bother her in the least. She pays us rent and has her chores just like everyone else. She has her own room with tv and comfy chair along with her bed (we converted our dining room for her as she could not do lots of stairs anymore), a bathroom, and another sitting area in our kitchen/breakfast area that overlooks the gardens and backyards where she can watch the kids play as well as a comfy chair on the front porch so she can sit out there--except during winter, of course--and watch what is going on.
Unfortunately she has reached the point where we can not leave her alone for extended periods of time as she could not handle it anymore if the toilet overflowed, the garbage disposal jammed, the lights went off, etc. So when we are gone on vacation and she is not with us, she goes to a nursing home for respite care. It is good for all of us--she has friends her age to interact with and we have peace of mind. She likes it there and that is where she will go when it is no longer possible for us to have her in our home.
If we had known about the senior housing, she would have had her own apt in a building with others her age, with activities throughout the week and on weekends, a bus to take them places, etc, and still been able to spend plenty of time with us and travel with us. She could have had a lifestyle similar to what she was used to before. Were there facilities near her home town? Yes, but I am an only child, there is noone else to help, and we could not run up there every time there was a crisis, so decisions had to be made. They were not made lightly.
The questions I asked are ones that I often get from others when they find out my mother lives with us, that come up often in discussions like this, that are in books about this subject, and that we had to answer and discuss when she moved in.
Now I will tell you that my inlaws will never live with us--per my dh's wishes--nor will they live with their other son and his wife. The havoc that they would cause would be too horrible to imagine.