you can't use the marriage registration, it must be the certificate... if what you get on the day of the wedding is a registration, it's not what they want and you must wait for the certificate to send that (copy or original)
check the country specific checklist to see if they require a copy or the original (i don't think they ever refuse originals... if they don't require originals it will specifically say COPY on the line item of the document... . if it says original on the line item, you must send the original.. if it doesn't specifiy (even if it says send copies up at the top), you may be requested to send originals if you send a copy... it's confusing!)