Transition involves everyone, but coming out is all about you telling some people about you. It is all about the fact that you are trans. Coming out is just something about your identity and involves no one but you (unless you have an external identity, technically, but let's assume we're not dealing with that). Thus, your coming out, not transition entirely, is all about you. Other people's opinions matter to me, too, but aren't going to stop me from transitioning and they will have to find out eventually, so if there is no other optimal time, just tell them all when they're together.