Since you and your wife are already enrolled under the scheme and you have “Certificate for Enrolment” duly attested by the DDO, therefore, you need not generate the same thing again.
You have already sent a copy of the Certificates to the Medical Cell, Finance Dept. bearing a Office Memo of your DDO.
You should only add new beneficiary following the same process, generate the certificate for new beneficiary, get it signed by DDO and send a copy to the Medical Cell.