If the children have grown up, married and have children, where and how do they live? Should they buy (or rent) their own place or stay with their parents? Grandparents can help to spend time with grandchildren, but there is a risk of criticism from them. What is the best course of action? Share your opinion in the comments!

It sounds like a debatable motion.
Anyways I have got the following things to say with points to back them up
Marriage is between two people with matured mind and sense of reasoning. Once a person is of a marriageable age, he should start making plans to settle on his own apart from the parents house. It is worthwhile and also of greater benefit to live on your own before or when you marry. So that you and your spouse can have some privacy. So many problems have been witnessed in families where the Children Marty and still live in the same house with their parents. Staying away from your parents house does not negate the fact that from time to time you will come and visit them so that the children can see and spend time with their grand Parents. Courtesy demands that. I wish to invite @charis20 @pato84 and @ladysheba1990 to drop their view on this subject matter as a comment