All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger.
It is impermissible to pray behind an imaam who seeks help from other than Allaah and calls upon the dead apart from Allaah. It is invalid to pray behind such an imaam, as has been advised by some scholars. Shaykh Ibn ʻUthaymeen was asked, "What is the ruling on praying behind the imaam who calls upon the dead instead of Allaah and circumambulates the shrines of the dead?" He answered, “Praying behind the imaam who calls upon other than Allaah is invalid because whoever calls upon other than Allaah is a kaafir (disbeliever) and such an act on his part constitutes an act of major disbelief that takes him out of the fold of Islam. It is impermissible for the Muslim to pray behind a kaafir.”
Moreover, Ibn Baaz wrote:
“When the person prays behind an imaam who commits shirk (associates partners with Allaah in worship), then his prayer is invalid as long as this imaam calls upon other than Allaah, seeks help from other than Allaah, or makes vows to other than Allaah. In this case, the scholars held that it is impermissible to pray behind such an imaam. It is impermissible to pray behind a disbeliever, and such a prayer is invalid. Scholars held different opinions regarding praying behind the faasiq (dissolute) imaam, but not behind the Kaafir (which is unanimously prohibited).”
We advise you, dear Brother, to strive in performing the prayer in the mosque whose people you described as "practicing the Sunnah and opposing all of these innovations and shirk." You should also gently explain the religious ruling in this regard to your parents. You are also advised to frequently supplicate Allaah, The Exalted, to bless them with guidance and to keenly show more dutifulness towards them. Hopefully, this would help them recover from their heedlessness and realize that they were wrong. You are not obliged to obey them with regards to praying at that mosque and this does not constitute undutifulness towards them on your part.
For more benefit, please refer to fataawa 82654 and 82989 about the religious ruling on praying behind an imaam who practices religious innovations and holds corrupt beliefs and to fatwa 84942 about the limits of the children’s obedience to the parents.
Allaah knows best.