Spiritual? Guardianship? Other? None of the above?
What is the actual relationship to your LO? Family friend? Family(like uncle or aunt)?
DH is Lutheran and I'm catholic but we did get married in Catholic church and we did agree to do everything in my power raise our children Catholic. I'm a bad Catholic and I applied those rules loosely. I'll try to raise them Catholic but really we just want our LOs to have some sort of christian background.
Anyway, why did you choose god parents? Or why didn't you have them?
DH has god parents which are his uncle and aunt and they were involved in his early childhood and still send him cards and gifts into adulthood. (ETA: Wait, I don't think DH's god parents are his relatives. I think it was a family friend. His god parents were invited to our wedding.)
My god parents were a family friend and I saw them when I was little but my family has lost touch with them. I'm not even sure if they were Catholic. I think they were but I have no idea.
As for guardianship if something were to happen to us, I don't think being a god parent legally requires you to be the guardian. So for us we'll have to agree on that when we make up our wills. They may or may not be the god parents.