Is it permissible to study Islamic sciences at an institute affiliated with a mosque that one's parents object to, while informing them that the mosque is only a place for reading the Quran?

It appears that the family's prohibition from attending the institute is due to their Sufi orientation and the institute being Sunni. Therefore, there is no harm in attending even without their permission, as long as there is no detriment involved. One can use ambiguity and equivocation when answering the family's questions, such as informing them that one is reading the Quran without adding the word "only."