I'm sort of confused.
First, I don't deal with facebook. I mean, I have an account, but it's not my main source of communicating. ESPECIALLY if you want to keep something a secret.
Second, I have received many friend requests.......from people I don't even know or that were related to someone I knew 30 years ago that I don't stay in touch with. I learned my lesson when I accepted a friend request from a guy I'd been friends with in high school. He was a family friend and we'd lost touch over the years. At first, I was glad to hear from him. AFTER accepting his request, I saw all the photos on his profile and I couldn't un-friend him fast enough. He's pushing 60 years old and apparently thinks he's some kind of "rock" god. Lip injections, wrinkles, long hair, and photos of himself with nothing but his guitar and a thong. GROSS!
Sorry for getting sidetracked on that note, but seriously, you can't assume anything when it comes to facebook. You don't have to accept friend requests. You don't have to use that as your only means of communication.
I just keep hearing of so much drama generated from facebook and in my opinion, it's just not necessary or worth trifling with.
Maybe I'm naive or old fashioned, but I don't see how anyone could expect to keep anything a surprise after posting on facebook.
Have a belated surprise and go about it in a different manner.
Sorry, I guess I gave you more than a penny's worth of my thoughts.
Best wishes.