So......Most of the laser tag kit you see out and about using a PWM-based signal at 38, 40, or 56kHz (choose your flavour wisely - it *will* affect availability of parts). 38kHz is most common for UK sourcing.

If you are just using a IR LED and not transmitting any form of modulating signal (just on or off), you *will* get stray signals from the Sun, your nearest fluorescent tube, etc, etc. I've been there and tried this sort of stuff before.

I do this sort of stuff (partly) for a living: including looking after a fleet of 24 laser tag guns and sensor systems, and fixing laser tag kit for other sites as well.

Happy to help if you need me to - just ask.