A girl’s father has performed upanayanam for his grandchild by considering him as his son. When his sons could not perform pitru karyam for him, can the daughter or his grandson perform the obsequies?

Only sons must perform such rituals.
Notes:
There is no need for the daughter or the grandson to perform such rituals, instead, they can sponsor food that is been distributed in the temple or they can take up some other kainkaryam.