All perfect praise be to Allah, The Lord of The Worlds, and may his peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
Sharia takes the intention and condition of the donor into consideration. Therefore, the authorized person or organization is obliged to abide by them as regards delivering the donated money to the eligible recipients . The Messenger of Allah said: "And the Muslims will be held to their conditions"{Bukhari}. Al-Imam Ashirazi said: "The authorized may not act save as told by the authorizer or as is customary because he is bound by the latter`s intention and conditions."{Al-Mohazab, 2/165}.
Accordingly, the acts of the above agency are bound by the permission of the donor. Therefore, if the latter authorized it to dispose of his donations as it sees fit then there is no harm in transferring them into its account which is beneficial to all eligible orphans.
However, if the donor has chosen to take care of a particular orphan on regular basis then his wishes should be respected and his consent should be sought before disposing of his donations. And Allah knows best.