How to Disciple a Pre-Christian

At what point did the 12 become Christians? Like at what point can we nail down their conversion? I think we can have a decent idea with some of them like Peter, but when is their conversion? And here's the crazy thing. It's not as though, unless you're going to argue that they were all converted minus Judas, 11 of them were converted at the moment of Jesus' initial calling. So how do we disciple our kids? We are discipling them as pre-Christians."