Ann,
A minor point, but Grand Master is not a title used at the lodge level; Master of the Lodge is the correct title. Grand Master is the title used for at the state level, meaning the temporary top official for Freemasonry in the state. I suspect your grandfather was Master of his lodge.
When I was Master of my lodge a few years ago, a long time member, a Catholic man, died and had before his death requested a masonic funeral service. His daughter, also a Catholic, called me for details about the service and ranted (really no other way to describe it) about how Masonry was despicable and that no Catholic should ever be involved with it, but that it was what her father had wanted and so be it. I did my best to console and comfort her, knowing how traumatic times of family deaths are, and assured her we would be respectful of family wishes. After our service the daughter came to me to apologize for her earlier stress related anger, and to say how moved the family was by the solemnity and reverence of the service.
You are right...luckily he turned Christian before his death, but before that Masonry was his religion.