Reading the original newspaper article, it seems the kids were acting as if they were signing up for the army. the reenactor put slave on the "occupation" line for a few of the black kids.
Seems to me like everything was known and above board.
You can get a bunch of laughs and good feelings by drafting everybody within earshot into the Infantry. Wisely keeping at least one family member with a camera out of the formation.
Adults and kids formed up and given a few basic commands and movements will suck them into the spirit of things, break the ice and step up the interaction in the other areas.
Sometimes the kids pick it up better than the grownups.
Two people can do exactly the same activity but it comes out 180 degrees different just based on their personality.
Just my opinion of course.
But all that is going to do is prejudice the black kids against the grey, and against symbols of the Confederacy, we'll give them a misunderstanding about what the war was really about. We know where the free black enclaves were in the Southeast, whats so hard with putting on that little form, it's not like this is reality anyway, that they're from said enclave, and giving them an occupation that would have existed in these enclaves. It gives a more balanced telling of the war, maybe even organizing a replica black unit, under the command of a black officer, all in grey, if we're going to give accurate history.