I was raised a Catholic, but have been an atheist for over 10 years. I've told my parents I am a "non-believer" and a "freethinker". They are aware I haven't gone to church in a long while, but we have never had an in depth discussion about my atheism - it would certainly sadden them.
My parents' 50th wedding anniversary is approaching. My parents informed me they don't want a big party or gifts, but they want the family (my brothers, sisters and a few other close relatives) to attend Mass together. Initially, I thought no big deal - it will be a private little Mass much like a baptism or wedding and I can just sit there quietly and passively observe. I cringed when they told me it isn't going to be a private ceremony, but part of a regular Sunday Mass. The family will sit up front and the family will participate (read some Bible passages, assist at Communion, etc.) in the Mass and a special blessing ceremony.
They have told me to arrive early and the priest will tell me what I am supposed to do. This conservative priest is an old family friend and many parishioners I knew as a child are likely to be there. I was an altar boy at this church many years ago as a child. Not going is likely to create a huge family rift. Should I go and say I prefer not to participate? - Mom is likely to cry. Should I go, participate, hold my tongue, go through the motions and shrug it off? I don't want to go so far as to feign belief and reverence, but I also don't want to ruin the celebration. Calling the pastor ahead of time is likely to be uncomfortable for me but I don't care about that. What I do care about is that it will definitely lead to future uncomfortable discussions between him and my parents. I certainly don't want him to lay some heavy Catholic guilt on my Mom for my apostasy. Any other suggestions?
It all depends on what is expected from you. If they just expect you to be there and not necessarily participate in overly religious symbolism or whatever then what's the big deal?
They want to have the celebration in church and they want you to be there, they'll have to make concessions just as much as you do. If they are going to force stuff on you, then you can remain calm and nice and tell them that you will not do so because it does not confirm with your opinions on the matter.
You can explain by saying that it would be similar to them to profess that Mohammed is a holy prophet etc.
It's hard to say what you should do, since it really depends on what matters more to you.
That being said, it seems to me that you should at least tell your parents the extent of your atheism, and let them know that you do not want to do something that would contradict who you are. I would not outright refuse to go to church, but clearly define what you are uncomfortable with. Of course, that entirely depends on what they are expecting and what you find comfortable.
Like in my case, I have reached sort of a compromise with myself that I would bow my head during prayers, but never recite any words. That feels right to me, but every person is going to be different about what they feel comfortable with.
The last thing I want to say is that you should understand that if a rift occurs in the family, that is not your fault. You are not the one pushing them away, and you are not the one asking them to agree to things that are uncomfortable to them. There is nothing wrong with giving in to maintain a peaceful relationship with your family, but there is also nothing wrong with standing up and saying "no."
I hope it all goes well.
As a recovering Catholic myself, with the rest of my family still very much Catholic, I may be able to help here, but it all depends on how devious you're willing to be. I'm a pirate, after all, and therefore have the sketchy morals of an all meat sandwich so I have no problem doing the following:
Mince words and turn their faith to your advantage.
What I mean by that is this. As "Good Catholics" they have to abide by the sacraments. As "Good Catholics" they have to realize that if you have not recently and regularly participated in the sacraments (esp. confession) that you technically should not have anything to do with communion at all.
Also, if you word it right, you can save face for both sides and they are free to think whatever they want, but really can't force you to do anything more than show up, sit, stand, kneel when appropriate and that's it.
I would say something along the lines of, "I'd be happy to go and celebrate your special day with you." and if they ask you to do a reading or otherwise participate in the silly rituals say something like, "I'm sorry but I just don't feel like my faith is strong enough to allow me to do that." They like it because it sounds all humble and respectful and shit, but really... of course your faith isn't strong enough - you don't have any!
Anyway, that's typically how I wiggle out of church obligations without stirring up a nest of religious zealots trying to "save" me. Hope it helps a little. Good luck!