That's your opinion. Not mine.
Cut the comment down to size for practical purposes
Ok.
I too am a Christian, and I don't think, like many others, that it is unreasonable to go to the civic office and sign a piece of paper to legislate your marriage. In fact, it seems like common sense. And while it is true, for centuries, this wasn't the case. You know what else wasn't the case for centuries? Secularism.
If you want to keep marriage in a secular state, you need to take it away from the religious institutions and incorporate it into the governmental ones. Religious laws should have no influence on government laws and so you can't expect for your marriage to be recognized LEGALLY if it is done in an institutions whose laws don't matter. The fact that you have to sign a piece of paper has no bearing on what so ever on who the state allows you to marry or not. You can marry whomever you want. Honestly. The clerk over at the civic office won't deny you to marry whomever you want. This is liberty in a civilized way. there is also liberty in a barbaric way, but we moved on from that one a long time ago. The state isn't involved in dictating who you can marry and who you can't, it's just there to observe and put on paper the fact that you are married. That's it.
If you want to have a society where the religious laws dominate your life, go live in one of them islamic republics. Over there, the word of islam is the law. Or go live in the Vatican if you want a Christian theocracy... though it can be kind of hard to become a citizen of the Vatican. In our world, the west, secularism exists for a reason and in a secular society, you solve your legal activities through the state. And in a civilized society you do the same, you don't sort it our yourself.
Your arguments about the "quaker vows" or whatever are not justifiable in any way. Just because you announce something to be so, doesn't make it so. You can say you're married to someone as much as you want, in legal terms, you aren't. Maybe in the USA, this is permitted still in some states, i can't say for sure. I'll tell you for sure where that isn't the case, the rest of the western world.
As for married in the eyes of God. Yes. I agree to that. Weddings in a Church are about being married in the eyes of God. Same for marriages done in all religions, it's to make the union of people valid in the eyes of their respective gods. Sure. Nobody is denying you to get married in a church and have a priest officiate it. But it has no legal value. None. And while I can't speak on the part of your grandparents, since I don't know the whole story, it seemed rather silly that they wouldn't get a paper from the civic office. And yes, its required. It's pretty much mandatory if you want to be married properly. Again.
Paper from the government for marriage = mandatory if you want it to be legal ; This is why agnostics and atheists can get married.
A religious ceremony = optional if you want it, and even more, it varies according to each persons' religion.