A movie house, for better or worse, is a worldy place. Full of all base notions. Cheap vulgarities of all kinds
Please don't dignify it with the term Mandir!
It sends the wrong signals to the larger society
An alternative I suggest is - "Chitra Bhavana"
Mandira in sanskrit merely means "place/abode". Not necessarily always a temple
But in modern Hindi / Prakrit languages, Mandira is the term for "temple".
So it's problematic to use it in a secular context