Something that departs from normally held beliefs (especially religious, political, or social norms) is heretical. If your family is resistant to change, they may consider your idea of making pancakes for dinner to be completely heretical.
Heretical is the adjective form of the noun heretic, which comes from the Greek word hairetikos, meaning able to choose. What is considered a heretical point of view can change over time. Examples of positions that were once considered heretical but are now accepted as facts include: the Earth is round, the Earth circles the Sun, and a little bit of chocolate is actually good for you.