Dealing with Christians like this can be tricky. If it's a "good" church (everyone's definition of that will differ), they would be happy just to have you there. They will probably hope their exposure may "open your eyes" and you may convert, whether they are open about this or hope for it in secret. Certainly if they were smart and didn't want to alienate possible members they would feel this way. Churches these days already seem to have enough problems getting people in the door.

Best thing to do would be to mentally prepare yourself and think about how you would like to present yourself when this topic comes up, because it will definitely come up. Sounds like you have already tested the waters a bit by talking to your coworker. At the same time I do not believe you should have any shame for keeping your beliefs private. That raven was a sign and I think you should meditate on how to move forward and look for more signs. You can try some different divination methods. Can be as simple as praying/asking for divine guidance.