In the context of Health Smart Homes for aging and cognitively impaired people, the adaptation of the smart assistance to the set of sensors/effectors and to the people present is a crucial problem. Some solutions have been proposed. They can either assist a lone person for a small set of activities in a precise smart space, either assist a person in mobility. However, to our knowledge none of them is able to manage the simultaneous assistance of multiple persons in different smart spaces. In this paper, we are considering this problem. We are proposing a multi-part solution to manage a truly ambient intelligence system. Based on a scenario of daily living in such a situation where conflicts in assistance may arise, we propose to use nested and explicit multi-agent organizations to help to "solve" this problem. After defining the concept of nested organization, we illustrate how it can be used to manage dynamically every aspect of multi-person assistance in daily-living activities in a Smart Home.