If you are in CotFSM because you really believe that the universe was created by a pile of noodles and meatballs, then maybe you have emotional reasons to hide the fact that you have a different theistic god than your family.
If you are in CotFSM because you believe that religion should not be taught as science, or that faith in family bonds and history is not nullified by, nor nullifies, scientific knowledge, then there is no reason for there to be emotional friction over your participation in a bit of fun.
FSMism does not necessarily negate the usefulness of cultural bonds and stories. It does realize that any format of cultural story is about as good as another at making people feel like they belong to the culture.
The open letter to the Kansas School Board did not demand that christian faith was irrelevant. It merely demanded equal time for something equally and totally irrational, thus putting the board members in a position of deciding whether total irrationality belonged in a science class in the first place.
You can be a christian and an FSMist, or a buddhist and an FSMist, or whatever. Balanced Rock, Utah, stands there single-boulderily proving that the Bible isn't literally true -- a worldwide deluge would have knocked it over. Diatom layers in Japanese lakes (which were never scoured by glaciers in the last ice age) show that some of those lakes have been there for over 70,000 years at least. The most you have to admit to your family or your religion is that you consider the cultural tales to be just that: cultural tales. You don't have to say those tales are invalid teachers of morality in order to prefer science as a method of explaining the progress of reality. Many populist evolution and old-earth proponents are still religious people and continue with their religious practices out of respect for their family history and bonds. They just don't pretend to think the earth is 6015 years old.
If what you are really hiding from your family is that you are an atheist, then that is a completely different thing. Back to you...
In case you didn't realize it, I DO have a sense of humor. How about you?
"I will not fear. Fear is the mind-killer... I will face my fear. I will let it pass over and through me, and when it has gone, only I will remain." --The Bene Gesserit
"Time is a spiral. Space is a curve. I know you get dizzy, but try not to lose your nerve." -- Neil Peart
"I'm not in the ship. I am the ship." -- River Tam
"The truth is simple. It's the lies that get complicated." -- me
"No matter where you go, there you are." --Buckaroo Banzai