In principle teaching children to donate food to a food bank, or donate to any other charity is a good thing, but unless you also teach them that donations should be made privately and who has given what or how much or and is not to be discussed at all, it can create difficulties for families who cannot afford very much.
However, my experience going round with a collecting box for various charities is that the poorer households are much more likely to give, as they know what it feel like to need help. Some apologise for not being able to give more. In the well-to -do areas I have had doors slammed in my face or been told, "We never give to charity!"