Signing of ordinance certificates

We have a new family that just moved into our ward. Their baby was blessed by his father about a year ago in a different ward than the one they were living in at the time. The baby's grandfather is the bishop of that ward, was a witness to the blessing, but the blessing was performed in his home and not the church in a regular sacrament meeting. The baby's birth and blessing were never recorded in either ward, so now that they are in our ward, I created a record for the child, recorded the birth and blessing, and printed a certificate. My question is, who should sign the certificate?? The bishop of the ward they were living in at the time of the birth and blessing, the bishop of the ward where the blessing physically took place (the grandfather) or the bishop of our ward where they now live??

Any help with this question would be greatly appreciated. Thank you.

I would give them the unsigned certificate -- OR -- If they are not requesting a certificate, I would instead give them the child's IOS for verification. In my opinion, many members are too catholic/protestant if they believe such blessings are saving ordinances.