Removing iCloud Activation Lock

I bought iCloud locked iPads from Goodwill (not knowing they were locked) to give to needy kids and special needs adults. I have receipts from Goodwill, what do I do?

These users don't care about the latest OS or new apps. They just need a portable browser for cloud learning, and these iPad mini's and gen 1/2 units are perfect. I tried calling Apple, to no avail. Original receipt required which I do not have since they were donated to Goodwill from all over the US.

Any suggestions?