Is it permissible to donate a water cooler on behalf of oneself, one's wife, children, deceased parents, and siblings?

Giving charity on behalf of the deceased is beneficial for them, by consensus. As for giving charity on behalf of the living, there is a difference of opinion. It is not a condition that the charity be for one person only; rather, it is permissible for more than one person to share in the reward of a single act of charity, for Allah's grace is vast. What you have done is hoped to be beneficial for you and for all those on whose behalf you gave charity.