This person wasn't someone on my own FB page. It was my fiance's ex. When we told the kids, they told their father. Whether I had a FB account myself would have no bearing on whether this would happen or not.
People are asking questions now, but there's still a lot of confusion. I used to think it was cool how big my family was. Now I realize the error of my ways, but I still had a pretty decent support rate. Out of about 150, there's only been 1 so far that says they're supportive explicitly, but isn't supportive in what they say. With a family this size, there's no way to come out without telling the whole town. If I can't deal with the attention, I would consider leaving the area, but I'm not making any drastic decisions about that just yet.
For the actual FB account, what I did was to create a second page and friend everybody I told. Then I removed them from the old page so I know who's left to tell. My FB is limited to only family and friends. Nobody on there is anybody I don't know or trust.
Luckily this happened now when I'm mentally prepared to transition instead of last year when I probably would have crawled into a hole instead. The only thing stopping me right now is I don't know which comes first, the RLE or the name change. I'm otherwise ready to hit the ground running.