As already mentioned, the gravitational forces arising from the interaction between the falling objects would be very small when compared to the weight forces acting on them due to their interactions with Earth. If you wish to include that in your calculations, then, since they are dropped from points 5m apart, you should also consider the fact that the value of g may be very slightly different for each one, and that the direction "vertically downwards" may also be very slightly different for each one (which would be true even if the Earth was a homogeneous perfect sphere). That's the problem with not neglecting negligible effects - you open up a can of worms!

The gravitational forces acting on the two objects due to their interaction when 5 m apart have magnitudes of approx. 2.7e-2 N, giving initial horizontal accelerations of approximately 2.7e-8 and 2.7e-6 m/s^2. In the 1.49 s it takes for the two objects to reach Earth, those accelerations will change negligibly. The smaller mass will travel along a very slightly longer path but will have a very slightly higher average speed - why should the horizontal acceleration affect the vertical acceleration?

At a latitude of 45 degrees, the value of g varies by approximately 0.001 m/s^2 per degree latitude, which means that, if one mass is dropped from a point 5 m further north at that latitude, then its value of g will be roughly 4.5e-8 m/s^2 lower than the value for the other one, and it will hit the ground very slightly after the other one. 

That's if one doesn't hit a can of worms.