Is it permissible to mix the funds of charities designated for daily Iftar for families during Ramadan, and what is the impact of that on the reward of the donors if the money of one of them runs out without their knowledge?

It is recommended for a Muslim to give charity every day, based on the saying of the Prophet, peace and blessings be upon him: "There is no day upon which Allah's servants awaken but that two angels descend, and one of them says: 'O Allah, give recompense to one who spends (in charity),' and the other says: 'O Allah, bring destruction upon one who withholds (charity).'" If a group of people share and combine their money and give charity from it daily, they will attain this virtue, because shared money means that each of them has a common share in it, so it holds true for each of them that they have given daily charity.