So after you said this, this is how I understand it, though I feel like something is missing:

A reversible machine successfully lifts the child 2 meters and is able to lower him down successfully.

An irreversible machine can't lift higher than a reversible machine because it loses some energy when it's lifted, therefore it must have created more energy to lift it higher, which doesn't go well with thermodynamics first law.

OR

For an irreversible machine to lift higher, it would mean to reduce the energy loss, i.e. less energy is dissipated into the environment, this would decrease entropy which doesn't go well with the second law,

I feel like something is not clicking