I use CS occasionally in my eyes, but it is 10PPM Ionic.
What you have is different because of particle size. Whether it makes a difference, I don't know.
I hesitate to recommend anything for children. For the grown up, they can do research, think on it and come to a decision on their own. A child can't do that.
You might try the sublingual route where it goes directly into the blood stream. Don't have a clue if that would help with the eyes, but it wouldn't hurt the child.
Have the child hold a tbl spoon of CS under the tongue for a few minutes. Repeat several times