I don't think they should be proud to pay children to make a slave work
I'm not sure if you can call vlogging or other forms of crypto promotion actual slave work because the working conditions are much different than hard labor or sweatshops. Plus you could argue that they are giving children an opportunity to learn valuable social skills and earn money for their future education.
A child has nothing to do in a environmental work, it's not his place. His place is at school, practice a sport, to get fun, etc otherwise personal development cannot be done properly. I talked about children working to mine gold, they don't have an education and it will cause them problems when they will be an adult. Shit jobs, a not so good social circle and so on. Education is everything, in some countries you are recognized and respected depending on your level.
To learn valuable social skills? Oh man, they don't learn anything other than spamming the web, and there are far more important things to learn. They probably have no idea how laws are created and voted, and by who, in their own country.
By children, around what age range are we talking about? 8 - 10 years old? 12? Either way, I think it's horrible that this kind of practice is being tolerated in some countries - good working conditions or not. Children are not meant to be used for labor. It's never going to be okay whether it involves manual labor or simply an online task. This is parallel to slavery - almost even worst. Countries where this is being practiced should strictly enforce laws against child labor whether its tier 3 or third world or whatnot.
15-18? At 18 you are still a teen. But I know some are under 15