Yeah, that can be a difficult one.
It is always adviseable to seek advice from a spiritual father tha understnds your situyation. It's not a one size fits all.
EC: it's not always as easy as "why would you want to". Sometimes there are things that happen at a parish other than marriage and the big ones that are important to the family even if you (I) don't personally get it or find it important.
Every individual has different family dynamics they have to deal with. I love that someone wrote "Honor thy Father and Mother" Obviously we don't do this to the peril of our soul but at the same time, I can't say that going to my parent's new Church dedication ceremony was at the peril of my soul.
I will say, that over the past 10 years, I have had to set boundaries as my parents grew comfortable (not happy, though) with my decision to leave the Lutheran church. For the first year I went to Lutheran Easter with my family because it was so hard for my mom. For many years I traveled for Christmas and went with the relatives to their Church... MAYBE making it to mine.
That's not recommendable in general but for me it did bring me to the point where I now never go to non-Orthodox Easters or Christmases and in such a way that it wasn't like taking a 2x4 to my mom's head.
When I got married and especially as the 1st child was coming, I sat down ith mom and explained to her that there will never be a time that any of us miss Church in order to go to a Lutheran service. That our child is being raised Orthodox and we will not confuse him as to where and what Church is. I think that was/is hard for her, but she saw that I was honest in this and respects it a great deal. Obviously funerals and weddings are still a different story, but this is how it is for us and this is OUR personal story. Everyone's is different.
My advice is 1) as everyone said: talk to a spiritual father and 2) ALWAYS go to a non-Orthodox service RESPECTFULLY (this is why I work hard to avoid guitar services because it is difficult for me not to sin by disrespecting in my mind what is for them a heart-felt service that I am sure Christ appreciates because of where they're hearts are) 3) with a critical mind about EVERYTHING (that doesn't mean criticizing, but rather never assuming anything said is approved by the Church, unless it obviously is) said 4) working hard to appreciate the Orthodox things that are said (this helps with #2) and 5) with one foot out the door mentally speaking - that is, not worshipping with them, but not drawing attention to yourself either.
That's a hard balancing act to follow so because of that it is always advisable not to go to non-ORthodox services ever... even funerals. But adviseable is not always what is practical nor is it always what is best for your soul and the soul of others.
I hope that made things clear as mud because that's about how clear this issue is in real life.
Josh