In my case, I told my wife first, because not being the first to know would have been unacceptable to her, and it was important to me to have her on my side. For everyone else, it came down to how much I could trust them not to blab. I very much wanted to be the one to tell people, not have them hear by gossip. So people I trusted got told earlier.
I made sure to map out possible connections where gossip could spread. For example, someone in the concert band was also in the dance class. So those groups had to be told at about the same time, or everyone would find out by gossip.