I was in the same situation - my guy and i wern't so into the idea of marriage for many reasons, but we decided to go for it as it was the only way for us to live and work in the same place. At first we told only our immediate family and REALLY played it down, but we found this was not really possible because our close family wanted to be happy for us and excited, rather than thinking of it as a mere formality. In time (ganted, a short time, as it was 3 months between decision to marry and wedding), our attitude changed a bit. there were certain pricples we would not let of of, such as we would NOT have a church wedding and i would NOT wear white, but we let our close families be excited for us and tell their friends and let them think of it they way they wanted to.
In this time, my parents told my grandmothers and aunts and uncles that i would be moving to England. Well, some people somehow knew how difficult immigration can be and started asking questions, as they knew i had a boyfriend in england. some even began to ask if we would be getting married. depending on how close your family is, it may be hard to keep up the lie. it is likely some of your close family will want to go to the ceremony and then they are put in the position of not telling others about the wedding.
I know its a hard thing, but i found that in my situation, it was easier to come clean, but that was because my wedding was to be in London and it would have been too much on my family to have them lie to their families and friends about why they jetted to london for a quick weekend. I dreaded telling my grandmothers that I was getting married but they couldn't come, but they were in the end supportive.
And as has been already said, you can have two weddings.
