Does anyone here know if "Fair-Trade Coffee" makes a real difference for the growers?

Who knows? But it would offer consistent work through some kind of government partnership agency for the worker. It's also supposed to prevent child labor violations but in those countries, everyone works from the time they are old enough to carry something.

They also have Fair Trade Cocoa grower/harvester programs.

Peter Singer and Jim Mason investigate this question in their book on The Ethics of what We Eat. They conclude that it does: Wages are slightly higher, and working conditions better (no corporal punishment, no child labor, no forced labor, better work safety, freedom to organize unions). I trust Singer's research assistants. Whether that's close enough to "knowing" for your purposes, or if it's just "blind faith in Singer's research assistants", is for you to decide.

Good enough for me!

Thank you Punkey, also.