There is no puzzling. There are no potential recipients left who were slaves. The government did not actively enslave anyone. There is no way to accurately account for the individuals who were slaves, as census records were spotted at best. And finally, I have no desire to be given something for nothing; and I have no desire to be the recipient of blood money.
If you have the measure of guilt that compells you to pay something to someone, then find a suitable charity and give them whatever you want to give them. It's even tax-deductible. But don't you dare tell anyone else here that they've got any obligation in that regard - and especially not on my behalf.