At first we did not think we would tell anyone that we were getting married in Canada earlier, but now we've let it slip to a few people and it doesn't seem to be a big deal. My mom knows, and if she's not ok with it she hasn't really voiced it. I think she sees and understands all of the planning that's going into our resort wedding and knows that THAT will be the real day.
I think because we're kind of keeping it quiet, and making the actual 'Mexico wedding day' such a big party that no one will really know the difference, or care.s To us, August 19th in Mexico is our anniversary, we're just signing papers beforehand. In August is when we'll start wearing our rings, and be married. Only the two of us will know that we're sneaking away somewhere in July for a romantic weekend, but although others know we're signing the papers then, the marriage is in Mexico.
I'm sorry I can't help with the beach bash, but I do think a few others have looked into it/or are doing it, so hopefully they can put in their 2 cents.