Because this is a long-form article designed for search intent, we must assume that the user typing this keyword is looking for . The phrase combines three powerful Japanese social concepts: Shinseki (relatives), Kodomo (child), and Otomari (sleepover).
The keyword searcher needs to remember: Dakara (because they are family) does not mean Gisei (sacrifice). You are allowed to protect your own mental health. "Shinseki no ko to otomari dakara" is not really about a child. It is about the ghost of Japanese collectivism haunting the modern nuclear family. shinseki-no-ko-to-o-tomari-dakara
Proper Japanese would be: Shinseki no ko ga otomari ni kuru kara, taiben da. (The relative’s child is coming to stay over, so it’s tough.) Because this is a long-form article designed for
Because health is a legitimate, face-saving reason in Japan, the shinseki cannot argue. Alternatively, offer a compromise: "I cannot do otomari, but I can watch them from 1 PM to 7 PM." You are allowed to protect your own mental health