Have you modelled/estimated the force that will be needed to move the wings up and down? (Which will be dominated by the air resistance, I assume, but the weight and inertia of the wing structure may also be non-negligible.) I think you should start with a quantitative estimate of the torque you need from the motor, then take it from there.
As a side note, it seems that your mechanical design can only flap the wings up and down. Don't you need some degree of freedom to tilt them (for less air resistance) before the up-stroke, then tilt/twist/rotate them back for higher air resistance before the down-stroke? Or maybe I have overlooked a degree of freedom in your model.