The marriage certificate should have been notarized when you got it; it's just a signature on the back of the certificate with a bunch numbers and a signature. The birth certificate needs the same thing. That can usually be done where the birth certificate was issued, if not they can tell you where to bring it to do that.
He can then send these to you to get them translated, but I would find someone to do it in the DR, it is less expensive. If nothing can be done in Puerto Plata, take a bus to San Francisco, it's a lot closer than SD.