Interactive Butterfly Trees - IR

Building an interactive art installation. Here I am working on separate IR Emitter/Receiver circuits (w/PCBs), that trigger a group of LEDs on or off. The project: A large, 8’ x 10’ LED interactive art installation. Theme is a grove of trees that are covered in butterflies and leaves made from dichroic plastic. Each “butterfly” has a group of LEDs built in that turn on as a viewer gets close. Built in to the branches of the installations “tree” structure will be a bunch of IR Emitters, needing to signal out to a distance of about 3-4 feet. Individual IR Receivers (built into each separate “Butterfly” ) trigger a group of 4 LEDs on/off as viewer walks into and bounces the IR signal. The hardest part of this project will be building a small (~1” x 1.5”, leaf-shaped) circuit and creating the PCB for the IR EMITTERS, operating at 38kHz. I would like to use a small microcontroller chip such as the ATtiny 85 so that the IR can operate stable at the right frequency and pulse for the proper time. Need help with the code to program the MCUs. A second circuit and PCB would also have to be designed for the RECEIVERS (~1” x .3”, shaped like the butterfly body) with transistors triggering a load of 4 LEDs (3mm) when IR is detected. I have mostly finished this one, though there are a few questions still. Power Management for the whole network of transmitters and receivers. I am envisioning approx. 800 total “Butterfly” receivers built into the overall installation and the appropriate amount of transmitters for each of the branches. Lots of power management. I am considering using PIR motion sensors/relays to turn on/off power for each “tree” so that it can be on standby should no viewers be around.