Whole bunch of ways to make this happen depending on how complicated you want to get, so lets start figuring out what you want to do.
The audio files option, how many sounds do you want? do you want to trigger them manually? are they groupable into sets you are going to shuffle? How long are they? do you want to play multiple sounds simultaneously?
For example on my robot goose, he has goose honks when driving, angry honks when spinning, and these are triggered on a shuffle play automatically when moving, he also has a series of national anthems that can be manually triggered. He uses one of these boards which gets commands from a microcontroller (any arduino/microcontroller will do), the speaker is just a standard portable speaker wired into the wavtrigger.
There are a bunch of cheaper options for sound boards of various complexity
The microcontroller in my case reads off sensors on the wheels to determine speed and motion, then sends commands to the wavtrigger to play audio tracks that are stored on an sd card.
For the bluetooth option is this just for streaming audio so you’ll use your phone to control it?
This can be as simple as a bluetooth module and an amplifier hooked up to your speaker. Motion sensing could get a bit more complicated but you could go as simple as a switch you stand on on the deck that then applies power to the bluetooth module.