I think ill try the electrical tape - IR is NOT heat. (take a quick look at wikipedia at the EMS, IR has SWIR (750-2000nm, these LEDS are probably in the 800-850 range similar to the best response of the CMOS sensor) MWIR (2-7um) and LWIR (7-20um) LWIR is 'heat' and requires a FLIR camera (or Seek) to view it. LEDS emit almost 0 LWIR.
Electrical tape seems to work for most users. And correct, the IR illuminators detect wavelengths of light outside of the range of the human eye (i.e. infra red radiation).