And, although I am separated from my husband, I still give presents to my nephews and nieces - not to buy their love, but because I love them. I think Gary alluded to a good compromise between his kid's tzedakah, and Marjorie's issues. My daughter also gives her toys away for tzedakah. She does this on her birthday and at Chanukah time. This is the clearest and most essential way for her to understand the meaning of tzedakah.
Money is still an abstract concept.
Giving food is good and understandable, but it's not as personal to her- her parents shop for the food, and give it to her to donate. Hannah can with her own direct sacrifices make these children happier in a way that she can understand. I would do nothing to discourage this impulse. We take the toys and stuffed animals that Hannah has selected and give them to a shelter or hospital. Hannah knows that children who are too sick to be at home can play with the toys until they are well enough to go home.