Is it permissible to pay monthly salaries with the intention of both Zakat and Sadaqah to the children of a deceased brother and his two wives, and to an orphaned and ill paternal aunt, and to an orphaned daughter of a paternal aunt, knowing that the amount paid far exceeds Zakat many times over?

If relatives are poor, they have a greater right to zakat (definition), and giving charity to them is both an act of charity and an act of maintaining kinship ties. It is permissible to increase the amount given as zakat with the intention of it being additional charity, but it is not permissible to give money with the combined intention of zakat and charity, because the intention for zakat must be purely for the obligatory duty. It is necessary to re-issue the zakat for past years with the sole intention of it being zakat. It is not permissible to delay the payment of zakat after its due date (hawl), but it is permissible to pay it in advance in installments during the hawl.