Here's what happened in my family. A Godfather was selected and the baptism took place. That man 'fell from grace' so to speak and we never saw him again. My mother asked another man to step in and act as Godfather to my brother. He's been in my brother's life ever since, attending all the important events and simply being a guide, a friend and sometimes a spiritual assistance. My Godfather was my father's boss. They split up their company and then the man died. I hardly remember him. My uncle took over and although I always knew he was not the official 'signature' on my baptismal certificate, he danced with me at my wedding as my Godfather and we had a funny joke about him 'making a deal they couldn't refuse' with all my boyfriends. Anyway, I think you CAN and SHOULD appoint a new person to take the role especially if it's an important issue in your son's life. We are Episcopalians too and it's always been my opinion that it's what YOU feel is right with your relationship with the Church that counts. Just do it.