Changed baby's name... help!

So we decided to name our baby girl Cecelia May back in October and announced it on Facebook in November to everyone with a picture of a banner I made. Recently we decided to change her name to Madelyn Cecelia. We're still not quite 100% about the first name but once we are I was wondering how to let everyone know. My baby shower invitations are going out right after Christmas and I'll be putting her name on them if we're sure of it by then, but not everyone can make it and is getting an invitation. I'm thinking of doing another announcement photo on Facebook with her new name but I have no idea what to say about the change! Does anyone have any ideas or suggestions?