Beware! Muah ha ha ha haaaa .... You will be known as that family member who only comes for the food!
Go, be a part of your niece's life and refrain from religious conversations. It's a one time event that you may regret one day. They're family. Love them for who they are.

I avoid family events as a general rule but wouldn't even consider attending an event forcing religion onto an unsuspecting child.

I think you should tell your basically tell your sister what you said in the post and ask her if she still wants you to attend, keeping what she knows about how you act and feel in these situations. If she still wants you to go, then go. I'm all for standing up for your convictions but there is something to be said for not alienating your family unecisary.

I guess it depends on how you feel about upsetting your sister. If it was me, I would go, sit in the back of the church, and not participate with the ceremony. I have done that at weddings and funerals, showing respect for the family and their beliefs without compromising my own. I think it would be fine to tell your sister that although you love her and the baby, you will attend, but will not be able to participate. Your hopes for the baby are reasonable, but, if you decide to attend, and go to the party afterward, I would not inform your sister of them, in what could be construed as confrontational. I would give her a card with a little note addressed to the baby from you with your wishes enclosed. If it is too upsetting for you to handle, why not tell your sister that you can't attend, and ask her if she would mind you just coming to the party? I think it is important to own your own feelings, and not use something like this to make a stand that would probably get you nothing but some hurt or bad feelings in your family. If you are a big enough person to be honest with your sister without rancor, perhaps you can both hold onto your own strong views on religion, and just have some mutual respect. If that won't work for you, maybe you should just tell your sister that you aren't able to attend. After all, the party is a celebration of something that is against your beliefs as much as the actual ceremony.

Go dressed as a priest, really do it up and treat it like an odd costume party - wear the biggest pope hat you can find! Never get invited again, problem solved.

I would probably attend to show love for family but in no way would I participate. Arrive late leave early enjoy the food afterwards. Enjoy seeing family.

With the exception of funerals of those to whom I have been unusually close, I always skip the religious observance but do attend the secular get-togethers afterward. Since I am open about my Atheism this has not been an issue with family or friends.

I am not just an atheist, but also a Unitarian Universalist (UU). Basically, this means that I do not care what religion people practice (including events they may hold being secular or not).

I do care whether it seems to be helping them to be good people. Atheism works for me, but some of my friends have rich lives intertwined with religion.

My advice would be to go ahead and think of it as frivolity and pageantry based in traditional practice and not irrational behavior. Not celebrating life because of others' comforting trappings sounds possibly irrational too.

My sister would’ve killed me if I had missed my nephew’s Brat Mitzvah.

There's a family reunion on Labor Day on my mother's side of the family. I used to go to church that Sunday with my mother, her sisters and a few other relatives. I went because the others were going and they served a brunch. They probably got tired of my, "this is my regular church" comment. Regular because I went once a year. Since Mom passed in 2015, I haven't been. One of the cousins is a member of that church and seems proud to introduce all her relatives. As near as I can tell, it hasn't harmed me a bit.

I usually try not to accept, but the cons of being young is that my family forces me to go to these events. No choice.

I usually attend but I don't participate. I try not to judge others to much about there choices. If you feel that strongly about not going they just don't go, I'm sure it won't be the end all be all for them.

I have attended funerals and went to hear my wife sing once. Went to a friends non denominational church once to look for more community opportunities. In each case I find it very hard to engage with someone who is sincerely telling me look at what GAWD just did for us with a straight face. As I am a guest in their place of worship its the kind of frustration of I would gladly unpack that with you at a neutral coffee shop, but this is not the place or time, so why am I here?

Yes I do attend at times

Yes I do attend at times

Family first. Principle is a great thing and should generally be upheld but when it's so rigid it divides good people then it might be time to re-evaluate.

It's a family togetherness event. No one is to be killed or maimed. This is just a disagreement in faith and lack there of. It won't make you change your mind, and you being exempt won't change theirs. Don't let it separate you from those you love.

And for family I'd suggest if you MUST tell her, please wait until after the ceremony. There is no good reason to ruin an occasion they wish to be a pleasant experience for all involved. Otherwise it would be better worth your time to just stay home.

Just look at it as another school play, an appallingly bad piece of theater which you attend anyway to show support for people you care about. Deal with it in the same way, go along, smile nicely and don't be the person who feels the need to point out every error and idiocy. It's not like it has any real effect.