Is it permissible to build a children's toilet on the upper floor of a mosque designated for Quranic education and occasionally for prayer?

Building a Quran memorization center above the mosque is permissible, and it takes on the rulings of the mosque. However, Sheikh Atiyya Saqr is of the opinion that once a place has fully acquired the status of a mosque, it is not permissible to build upon it, even for its own benefit. As for building restrooms above the mosque, it is not permissible, because the air (space) of the mosque is part of its foundation (bottom part). Therefore, restrooms should be built elsewhere, close to the mosque.