OP here: I asked 5 traditional priests, and 3 responded with 3 different answers. 

In any case, because of the muddiness surrounding the issue, and my personal discomfort, I informed the couple that “I’d forgotten we have a serious conflict” and cannot attend.

I did not feel it necessary to explain, since it is nearly certain they’d scoff at the religious objection.

Thank you for all your contributions.

If they scoff simply bear your cross. I think it would be good to speak the true reason why you won't come, it might even change their perspective.

As a side question, isn't IVF effectively murder? All the other fertilized eggs get 'destroyed' do they not? I am not too familiar with it.

A cousin of mine conceived via IVF.

Why'd your cousin tell you how they conceived a child?
Isn't it immodest or lewd going around telling people how one's baby was conceived? Implicit in saying one conceived via IVF is: "I masturbated" and "I killed several babies to obtain one live one."
It's like boasting ("coming out") that one's a fag.

Why'd your cousin tell you how they conceived a child?
Isn't it immodest or lewd going around telling people how one's baby was conceived? Implicit in saying one conceived via IVF is: "I masturbated" and "I killed several babies to obtain one live one."
It's like boasting ("coming out") that one's a fag.

OP here: Talking to them would do no good, they are so warped.  They think IVF science is glorious.  Shame never enters the mind.  It’s “medical” so it’s not self-abuse, they rationalize, it’s”a procedure.”  

The sin has been sanitized, and the shame with it.

As an example of how far gone they are, here’s a pic they posted on their Facebook page:

But according to that rationale, one couldn’t attend the baby shower of a single mother, without implicitly condoning extramarital sex?

So, if a couple is adopting a baby via arrangement with a pregnant young lady who can’t raise the child, going to the shower implies my approval of fornication, adultery, rape, or even incest?  Then I guess I committed a serious sin in going to the baby shower of an unborn child being adopted by the woman’s drug addict sister.  This child is the second such baby they’ve adopted.  The birth fathers and circuмstances of conception of both children is unknown.  DNA testing reveals only that the elder child is of Northern European and German heritage.  The second is German and East Asian, possibly Vietnamese.  The boy, baby no.1, is normal. The girl, baby #2 was born with brain damage and is developmentally disabled.  Both children are baptized and being raised Catholic.  
But even if not, I don’t understand not celebrating the arrival of a baby because of how he was conceived.  My only question for the OP is their association with the couple.  Is it a relative?  A neighbor?  Colleagues from work or school?  Someone from before you became Catholic?  Would you attend if you didn’t know about the IVF?  (I agree it is in bad taste to announce such a thing, but people these days have little to no sense of decorum.  A look on any social media makes that obvious.)
If the couple themselves disturbs you too much to attend, then at least send a card and a small gift for the actual baby.  

So, if a couple is adopting a baby via arrangement with a pregnant young lady who can’t raise the child, going to the shower implies my approval of fornication, adultery, rape, or even incest?  Then I guess I committed a serious sin in going to the baby shower of an unborn child being adopted FROM the woman’s drug addict sister.  This child is the second such baby they’ve adopted.  The birth fathers and circuмstances of conception of both children is unknown.  DNA testing reveals only that the elder child is of Northern European and German heritage.  The second is German and East Asian, possibly Vietnamese.  The boy, baby no.1, is normal. The girl, baby #2 was born with brain damage and is developmentally disabled.  Both children are baptized and being raised Catholic. 
But even if not, I don’t understand not celebrating the arrival of a baby because of how he was conceived.  My only question for the OP is their association with the couple.  Is it a relative?  A neighbor?  Colleagues from work or school?  Someone from before you became Catholic?  Would you attend if you didn’t know about the IVF?  (I agree it is in bad taste to announce such a thing, but people these days have little to no sense of decorum.  A look on any social media makes that obvious.)
If the couple themselves disturbs you too much to attend, then at least send a card and a small gift for the actual baby. 

NOTE BOLDFACE CORRECTION!  It was too late to modify!

First of all, how do you know 5 (!) traditional priests?  Wow. 

Anyway, I'd be interested in hearing the 5 responses. 

My gut thinks it might be best to skip the shower, but I don't agree that you shun the child/subsequent events once he/she is born.

I kind of agree that the couple are really low-class or ignorant to broadcast such a thing.  If that’s going to be the centerpiece of the shower, it wouldn’t be right to attend, but I would not shun the child for the sins of its parents.  If the child is a relative, that especially is not right.  Instead, I’d acknowledge the birth of the child and do I could to pray for the couple and see that the child is influenced to become Catholic.  Often, children end up leading the parents in such such matters.  

As for correcting the couple, that requires much prayer and wisdom. If you come on like gangbusters, it’s likely to make them think you bear hatred for the child, and from then on, your influence will be nil. A baby shower or family gathering of any sort is neither time nor place to raise the issue.  It sounds as if they are truly ignorant that IVF is wrong, that the male preparatory actions are wrong, that freezing embryos is wrong, and that “reducing” the number of babies conceived is wrong.  IOW, people raised without moral standards or with low morals are ignorant.  The same thing holds for someone who’s had an organ transplant or has donated their own or someone else’s organs in the belief that the donor is truly dead, therefore, it is a noble act.  

I have a cousin who had a double lung transplant.  (No, not Catholic.)  Do I rebuke her for being alive and refuse to associate with her?  You can’t undo a lung transplant.  (Well, you can, but the doctor who does it is guilty of murder and my cousin and those that approve are guilty of ѕυιcιdє or aiding in ѕυιcιdє and murder!)  What about her daughter?  Her grandkids?  Her husband?  These are not people I see on any kind of regular basis, but I’ve often wondered where to draw the line.  

Is it my duty to correct the sins of distant relatives?  What about getting a list of people who have designated themselves organ donors on their auto licenses?  I used to check people’s licenses all day when I was a cashier and they wanted to pay by check or credit card.  Should I have corrected or rebuked each one, and if that wasn’t feasible, quit my job?  

If even good priests disagree, what then?  I’m no moral theologian, but I believe the Church says a Catholic must follow the advice of his confessor or go with one’s conscience.  If a person has absolutely no idea, then he may safely follow the majority (Church) opinion. 

BTW, I’ve thought about it and I personally know a total of nine traditional priests, those who know me by name.  Unfortunately, three are deceased and three are stationed overseas on different continents, one is cancelled and is a hermit of sorts, location unknown since 2015.  That leaves two accessible, one a fifteen hour drive away, and the one whose Mass I attend.  He is located 2 1/2 hours away.  

These are hard situations for Catholics. Increasingly, modern culture expects us to compromise our morals and “go along to get along,” out of human respect. Those who resist are considered “puritans and prudes” (I hate how that term is always used to cast dispersion on the 6^th and 9^th Commandments) for not celebrating sin.  But every time we cave, we’re not standing up for God, and rarely does anyone get the message of fraternal correction.  

I think just sending a gift for the baby and skipping the shower is a good idea.