I'm sad that no one ever responded to this. I might be too late. I would definitely check with the OSU extension in your county. They can usually point you in the right direction for things like plant swaps. I would like to think that other Ohioans would happily donate things to the kids without asking anything in exchange. Or the kids could volunteer to do some yard work for people in exchange for plants.
My other suggestion is to call around to local nurseries. They often have things they can divide and part with. They will be more inclined to do so for a good cause.
Good luck!

If you're willing to drive a couple of hours, I have more irises than you can shake a stick at that I'm willing to give you. It'll be time to divide them pretty soon. The only other things I have in abundance are weeds, but I'll keep those for myself.