I would like to believe that AWB made plans in case he found himself incapacitated and had that card ready and waiting. I believe he either relayed the information to Blue, Jefferson or Henry. I’m leaning towards Henry as I prefer to think that AWB trusted Henry enough to follow through for him. They did after all have Operation Cobra going so why wouldn’t he ask Henry to send out the card once the curse was broken
Mary Margaret had a way with birds so it would make sense that her grandson would have the same gift. What a twist for Henry to have made contact with a man who could very well turn out to be his father.
I’m probably way off here, but still, it’s the way I’d like to see things turn out. I’d love to see Henry getting more involved.