There doesn't seem to have been a provision for age of informant:
1836 Bill:
https://ukga.org/index.php?pageid=33382
And be it Enacted, That the Next of Kin, or other Person present with or attending in his or her last illness, every Person dying in England after the said Thirty-first day of December, or in case of the death, illness, inability or default of all such Persons, the Occupier of the House or Tenement in which such death shall have happened shall, within Eight Days next after the day of such death, give information, upon being requested so to do, to the said Registrar, according to the best of his or her knowledge and belief, of the several particulars hereby required to be known and registered touching the death of such Person: Provided always, That in every case in which an Inquest shall be held on any dead Body, the Jury shall inquire of the particulars herein required to be registered concerning the death, and the Coroner shall inform the Registrar of the finding of the Jury, and the Registrar shall make the entry accordingly.
And even after the 1874 Act
https://www.legislation.gov.uk/ukpga/Vi ... 88/enacted
When a person dies in a house after the commencement of this Act, it shall be the duty of the nearest relatives of the deceased present at the death, or in attendance during the last illness of the deceased, and in default of such relatives, of every other relative of the deceased dwelling or being in the same sub-district as the deceased, and in default of such relatives, of each person present at the death, and of the occupier of the house in which, to his knowledge, the death took place, and in default of the persons herein-before in this section mentioned, of each inmate of such house, and of the person causing the body of the deceased person to be buried, to give, to the best of his knowledge and belief, to the registrar, within the five days next following the day of such death, information of the particulars required to be registered concerning such death, and in the presence of the registrar to sign the register.
I don't see anything there about being an adult so 14 was probably old enough