I have to visit my family in Minnesota this week?

They are religious fundies and I'm an atheist. All they really do at home is read/study the Bible and sing hymns, and they only leave the house to go to church (which is like every other day) Their kids are homeschooled because the parents don't want them to be influenced 'by the outside world'. They think their purpose in life is to not serve the society, but the Lord...Their only form of entertainment is reading books (they aren't allowed to watch tv, or listen to music) and the kids are so brainwashed and uneducated, it's sad, but my parents aren't giving me any choice but to go. My parents are also Christians, but they accept my beliefs. I know if I tell my uncle and aunt that I don't believe in God, they are gonna do everything in their power to convert me and make my vacation miserable. But if I don't tell them, I'll have to start living a lie in their house and since my parents know I'm not a believer, they'll lose all respect for me if I lie.. Advice?