You CAN NOT pressurize your water storage tanks with compressed air. They are not designed, nor certified as a pressure vessel. In this country, there are very strict standards governing pressure vessels due to the large amount of energy stored in the vessel with a compressible medium (such as air).
I have designed a compressed air over water system similar to what you are describing that operated up to 120psi. For the cost of a system like the one I designed, you could buy 100 water pumps and pay a professional plumber to install every one of them. The bulk of the cost will be in replacing your tanks with certified pressure vessels.