Hi, you there? You who found this site because you typed "revoke godparents" into Google?
Welcome. Y'all should form a club or something, because there are a lot of you.
So, did your kid's Godparents embezzle your money? Did they become atheists? Did they move to France?
Let me make this painless as possible. It will be quick, like ripping a band-aid off a hirsute woman:
"How can I change or remove people as Godparents?"
You can't.
The Church won't change the certificate or the record books. Sorry.
If it makes you feel any better, the role of a Godparent is to offer spiritual guidance and conversation to your child as he or she grows. They also serve as witnesses for the church records. Nothing more. Godparents don't get your kids when you die, nor are they on the hook for paying for the graduation party.
The Godparents you chose sound like lousy bastards who were ill-equipped for the job to begin with. So good riddance! Be done with them! I suggest you find more stable, church-going friends who your kid likes, and invite them to be "Spiritual Advisors" or "Pre-Confirmation Sponsors" for your child. Hell, call them "Godparents" if you want. Who cares?
Perhaps you could screen the unofficial replacements with questions like these:
"Do you ever plan to embezzle money from us, or have sex with my spouse?"
"Do you plan to leave the one true church for the fiery abyss anytime in the next 20 years?"
"Any plans to move to the Netherlands?"
That sort of thing. If they answer "No," to all the questions, then I think you're safe.
Then, as a last measure, give them this book:
It is an excellent resource and gives Godparents (and "Godparents") great ideas for initiating spiritual conversations and giving frugal baptismal-themed gifts.
You will FINALLY have people in your children's lives who will actually talk about God! Who cares if their name is on the certificate?
And the ex-patriot atheist embezzlers will never know. Unless you write them a letter telling them what crappy people they are...
But that wouldn't be very Christian of you, now would it?