No, there would be no measurable effect. But we can consider two things: force and mass.
Let's imagine we planned very poorly, and always landed our ferry craft in the same Earth-moon orientation (so that by landing, the moon was always pushed "away" from its current direction of motion).
The gravitational force between the Earth and moon (the force keeping it in its circular orbit) is roughly 2x10^20 Newtons. The force of a single "ferry" landing on the moon can be estimated... say it is Space Shuttle sized (100,000 kg), and it just lands vertically on the moon. Impact is about 100ms in duration, and change of speed is about 4m/s during that time (these estimates from the lunar missions) by the time it is near the surface. That's a force of 100,000 * 4 / 0.1 = 4 million Newtons.
How many landings would it take to be the equivalent of Earth's gravitational attraction? 50 trillion. Say we get really efficient at space flight, to the point that we can do as many trips to the moon as we have regular flights per day on the Earth... that's about 100,000 flights per day.
To make 50 trillion trips, it would take 1.4 million years.
The issue of mass has already been answered... such a small change in mass would result in an undetectable change in the moon's orbital velocity. But, to answer your second question, how much mass would it take?
Say we want to change the moon's speed by 10%. The equation for orbital speed is $v = \sqrt{\frac{G*M}{r}}$, where G is the Universal gravitational constant, M is the mass of the Earth, and r is the radius of the orbit. This means for v to change by 10%, M must change by 21%. Given the mass of the Earth, this means we'd need to move 1,500,000,000,000,000 billion kg of people and stuff before having to be worried. The average male is 70kg. So, to make a dent in the moon's orbital speed, we'd need to have 220,500,000,000 billion people here. Considering the Earth only has about 7.5 billion people, that may take a while.
The only thing that can realistically alter the moon's orbit is an impact with a large asteroid traveling pretty fast. Nothing man-made could really do it.