Praise be to Allah.
It is mustahabb to give charity to one who is in need, even if it is something small, because the Prophet (blessings and peace of Allah be upon him) said: “Protect yourselves from the Fire even if it is with half a date.”
Narrated by al-Bukhaari, 5564; Muslim, 1689
It was narrated that Abu Hurayrah (may Allah be pleased with him) said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “Whoever gives charity the equivalent of a date that was acquired by halaal means – for Allah does not accept anything but that which is good (halaal)– Allah accepts it in His right hand, then He tends it for the one who gave it, as one of you tends his foal, until it becomes like a mountain.”
Narrated by al-Bukhaari, 1321
Reciting du‘aa’ before giving charity is something that is subject to further discussion. This has been discussed previously in the answer to question no. 98579.
It is permissible for a person to give in charity on his own behalf and to intend that others among those who have died have a share of the reward of his charity. This has been discussed in the answer to question no. 102322.
With regard to giving a share of the reward for the charity to those who are still alive, this is not mentioned in the Sunnah so it is better not to do it.
It says in Zaad al-Mustaqni‘: If a person does any act of worship and dedicates its reward to a deceased Muslim, or one who is still living, that will benefit him. End quote.
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said:
If a person has died, and one does an act of worship on his behalf, that serves a purpose, because the deceased is in need (of hasanaat) but cannot do any righteous deeds. But if he is alive and is able to do this act, then in that case it depends, because it may lead to the living person depending on this man who is doing an act of worship on his behalf. There is no report that the Sahaabah (may Allah be pleased with them) or the righteous early generations did such a thing; rather what they were accustomed to do was to dedicate the reward for an act of worship to the dead; in the case of those who were still alive, they did not do this, except in the case of an obligation such as Hajj, because that was known from the time of the Prophet (blessings and peace of Allah be upon him), but that is subject to the condition that the person on whose behalf Hajj is performed is incapable in such a way that there is no hope of recovery.
End quote from ash-Sharh al-Mumti‘, 5/371
There is nothing wrong with exchanging pieces of metal for others; rather it is permissible for you to change your mind about this charity, because anything that is given as charity or a gift does not become the property of the recipients unless they take possession of it. If it has not been taken possession of, then the giver has the option to go ahead with it or to change his mind concerning it. See the answer to question no. 146237
The one who wants to give charity has a choice between giving it to one poor person or more, as he sees fit. It is better to give it to relatives if they are in need, because Allah says (interpretation of the meaning): “To an orphan near of kin” [al-Balad 90:15].
And because the Prophet (blessings and peace of Allah be upon him) said: “Charity given to the poor person is charity, but given to a relative it is two things: charity and upholding ties of kinship.”
Narrated by at-Tirmidhi, 594; classed as saheeh by Shaykh al-Albaani, may Allah have mercy on him.
And Allah knows best.