How do you politely say no to a charitable gift?

A group from work is trying to get Easter Baskets together for a homeless shelter in town. We contacted the shelter and they requested only new items for the children. I mentioned this to a woman I know who lives in another town (about 50 miles from me), and she has since been searching and collecting things around her home to donate to our project. I am touched that she is doing this and don't want to just flat out tell her no, but we can't accept these used toys from when her children were young.