"Child labor" is, generally speaking, work for children that harms them or exploits them in some way (physically, mentally, morally, or by blocking access to education).
Child labor is terrible for children's well-being.
Considering the context says "harms them or exploits them in some way (physically, mentally, morally, or by blocking access to education)," child labor being terrible for their well-being is definitely correct.
( z1 terrible :ARG1 ( z2 labor :ARG0 ( z3 child ) ) :ARG2 ( z4 well-being :poss z3 ) )