Nope! Getting an Income certificate will be required for the family. You can collect the document from the BDO/SDO and it don't take much of time. As your mother is a housewife and there is no income except the mention, then take the pension slip to the SDO and you will be issued the required certificate. For EWS certificate the Income certificate is important as you have to provide some proof in the Affidavit.

Wish you a great eve!