Hi :)
Years ago, I worked as a summer student for a charity and we received items of clothing. Those that we did not sell in the shop (proceeds went to charity) we passed on to organizations that were more than happy to distribute to the right places/organizations/people. Definitely donate them. A lot of charities work together, and with churches, etc. If you dispose in the trash, no one benefits compared to it going to a needy family. I always donate - unless not wearable.
Here's the other thing - at the charity place I worked, we had some powerful cleaners. We used to wash a lot of questionable items (they wanted to sell as much as possible, to raise as many funds as possible for charity). We were able to get out many baby stains - food, formula, .. a lot of times people use sensitive detergents now, but you can still get out a lot of stains using Borax, etc. and someone may be willing to go to the trouble.
And quite frankly, from a lot of the shoppers at our charity, they weren't super fussy. They couldn't all afford to eat, so a little light staining probably wouldn't deter them from clothing their babies.