Is it permissible to use the orphaned children's money to buy a motorcycle for the father (grandfather), given that he has become the family's provider after the husband's death, knowing that the mother will start receiving the husband's pension in a few months?

It is permissible for a woman to donate her private money to buy a bicycle for her father.

It is not permissible to donate or dispose of an orphan's money except in a way that brings them pure or predominant benefit, based on the Almighty's saying: ﴿And do not approach the orphan’s property except in a way that is best﴾ and ﴿And they ask you concerning orphans. Say, "Improvement for them is best."﴾

Therefore, it is not permissible to take the money of the two girls to buy a bicycle for their grandfather unless it will bring them additional benefit and clear advantage, such as increasing his ability to provide for them better.

And it is permissible for the poor guardian of orphans to consume from their money in a reasonable manner, to the extent of his need or the wage of his equivalent, whichever is less.