I'm keeping it a secret from everyone except my wife. I want to see how long it will take for people to realize if I don't advertise that I'm getting them to friends and family either in conversation or via Facebook.
Yeah, Carrie kept it pretty well under wraps before she got hers, too. Her sister and best friend knew, and my daughter and her husband, but that's about it. I don't think the rest of her (big Mormon) family knew until she posted a pic in their group text. Her sister-in-law just asked, "When did you get braces?" Carrie replied, "About a week ago. Fancy, huh?" And that was the end of the braces discussion in the group.
Carrie and I have a pretty broad social circle, so we run into lots of people who don't know she got braces, even now, a couple of months later. But frankly, after the initial "hey, you got braces" recognition, almost no one gives a damn. It's a WAY bigger deal to us here than it is to anyone outside the braces community.
All that said, neither Carrie nor I are enthusiastic users of social media. I seriously cannot remember the last time either of us posted on Facebook (I call it Boomerbook and only have an account because my job requires it), and she's literally never posted a pic on her Instagram account. Social media reactions might differ from face-to-face interactions. Will be interesting to see if your results differ.