I mean if the donation is unwanted, it is possible to deny it (you could even go the "we only want the containers" route). Or if the decision comes at a later p

I mean if the donation is unwanted, it is possible to deny it (you could even go the "we only want the containers" route). Or if the decision comes at a later point in time, one could ask the donor if he wants the stuff back (once again, possibly accompanied by "but we'd like to keep the containers").