If you want to look at energy in terms of personal output, I would offer the following:
-Energy required for your son to walk versus the energy required by you would depend on mass and form. The larger or less coordinated the structure, the more energy required.
-The total output of energy by some people can be significantly less depending on the amount of entropy in their system.
This is based on the first and second laws of thermodynamics, as I understand them. Though, I fully admit to my lack of study in this area.
First law of thermodynamics
-Energy can neither be created nor destroyed. It can only change forms.
-In any process, the total energy of the universe remains the same.
-For a thermodynamic cycle the net heat supplied to the system equals the net work done by the system.
Second law of thermodynamics
-The entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium.