Playing sound effects on an arduino is a huge pain. Playing sound from a raspberry pi is much easier. Receiving IR commands on a Pi takes a bit of work though.
For this part, I'm using lirc. I started with a clean install of the latest pi OS. I installed lirc, configured it for the default driver, and set the config.txt to read from the proper gpio pin. Then I tried to run irrecord. It failed. Over and over. So I found a config file for a similar remote and it worked just fine. I made a lircrc file with just one entry that will use irexec launch omxplayer when it gets the signal. That's it. When I push the remote button, the sound plays.
Next steps for this will involve not much really. Packaging I guess.