When filing a Certfication of Notice with an office of Wills, who should we list as the notified beneficiaries?

I am so sorry for your loss.  The Notice you speak of is notification to any beneficiaries (under a Will) or intestate heirs (those who would receive if there is no Will). Under PA. O,C. Rule 5.6(a) it is the following:

"(a) Requirement of notice. Within three (3) months after the grant of letters, the personal representative to whom original letters have been granted or the personal representative's counsel shall send a written notice of estate administration in the form set forth in Rule 5.7.

(1) every person, corporation, association, entity or other party named in decedent's will as an outright beneficiary whether individually or as a class member;

(2) the decedent's spouse and children, whether or not they are named in, or have any interest under, the will;

(3) where there is an intestacy in whole or in part, to every person entitled to inherit as an intestate heir under Chapter 21 of the Probate, Estate, and Fiduciaries Code;

(4) the appointed guardian of the estate, parent or legal custodian of any beneficiary who is a minor child under the age of eighteen (18) years;

(5) the appointed guardian of the estate or, in the absence of such appointment, the institution or person with custody of any beneficiary who is an adjudicated incapacitated person;

(6) the Attorney General on behalf of any charitable beneficiary whose interest exceeds $25,000 or which will not be paid in full;

(7) the Attorney General on behalf of any governmental beneficiary or in default of the other heirs of the estate;

(8) the trustee of any trust which is a beneficiary; and;

(9) such other persons and in such manner as may be required by any local rule of court.

I might speak with some one on this.  Good luck.