In this situation you will not be generating much electricity. First off air is not a good medium to transfer energy. second a single human standing, or walking on a pad will only weigh an average of 190 lbs or so. now if you transfer that to pressure pads all you gain is his gravitational force, or maybe a tad more, with each step, only 1/2 his weight.
The distance the pad could travel is very limited so even if he could generate more force, if you had a large travel in the pad, walking across your device would be uncomfortable at best, hazardous at worst!
You are talking a very low PSI of air you could possibly generate, and therefore a very low deltaT. It would take an IMMENSE croud of people constantly walking across such a device to get anything even slightly useful. and the complications of check valves, etc would make the build immense in cost.