For IR LEDs you have not only the wavelength of light, you also have a repitition rate. Typically you modulate the IR LED with a square-wave in the 10s of kHz; this lets you have a much higher instantaneous power with a much lower average power. If done right, it also means that 2 IRs with a sufficiently different clock-rate will interfere with each other less.

Based on our experience so far with the latest Oculus SDK, mounting a Leap Motion Controller onto a DK2 does not effect positional tracking, since the DK2 was designed to have more LEDs than needed for input experiments such as this.