What is to be done with the extra boxes of dates brought by charitable individuals to the mosque for the breaking of the fast by worshippers in Ramadan; should they be distributed to the poor and needy, or sold and the proceeds spent on the mosque's needs?

The original purpose of this date is for breaking the fast. If it is possible to use it to break the fast of fasting people throughout the year, then that is the designated purpose. If that is not possible and there is a fear of it spoiling, then it is permissible to give it as charity to the poor. If they are not found, it is permissible to sell it and use the proceeds for the benefit of the mosque, because utilizing it is better than destroying it.