I know on MN an expensive wedding has to mean divorce, whilst a cheap private affair means happily ever after. Back in the real world, it's absolutely not true.
It's got nothing to do with the money, people have drawn the wrong conclusion.
What causes a marriage to end quickly after the wedding is stress. If you get too stressed planning your wedding, become a bridezilla about the details, your marriage is likely to fail. Usually, that does also correlate to an expensive wedding though.
It's your wedding, it shouldn't be stressful. Have plenty of food, plenty of booze options and music, you're sorted. Have a small wedding with just family and a pub meal after. Anything in between or bigger or smaller. No one remembers the details except the couple. Just don't get stressed about it, it's one day. A marriage is no different to a girlfriend/boyfriend relationship, its just a piece of paper. You still need to work on both, a wedding doesn't make all your problems go away. In fact if you already have problems, it's going to make them show very quickly and make them worse.