(((Cordelia))) I would advise against destroying their faith, but at least get them started on the road to a different life. It sounds like they will still associate with you, just avoid religious subjects. They will bring them up, just respectfully ask not to talk about it. Ultimately, you can choose to betray yourself or be true to yourself.
Being true to yourself is going to automatically cause a lot of painful soul-searching by your parents, and they may diiscover that their "life" is not what they thought it was after all. Betraying yourself will bring everything back to a stifled normalcy, and your personality will be subsumed under the pressing burden of Organizational law and customary expectation all over again.
I'll be praying for you.
AuldSoul