You won't get diapers from WIC.
There may be a way you can get something else from WIC, if you explain that you do not use formula and that you won't be able to breastfeed. And you'll only get formula for the first year, anyway, and then you'll start getting food for the child. (Milk, cheese, etc.)
I don't think it's a bad thing to donate anything you don't use. It doesn't seem like stealing at all.
There may be a way you can get something else from WIC, if you explain that you do not use formula and that you won't be able to breastfeed. And you'll only get formula for the first year, anyway, and then you'll start getting food for the child. (Milk, cheese, etc.)
I don't think it's a bad thing to donate anything you don't use. It doesn't seem like stealing at all.