Well, while a 3-year-old might be a Mozart-level prodigy, most experts recommend waiting until they're a bit older before starting piano lessons. At this age, they're more likely to use the piano as a drum set, which isn't exactly conducive to learning to play Beethoven's Fifth.
But that doesn't mean you can't start fostering their musical interests at a young age! Singing and playing simple tunes on the piano together can be a fun way to introduce them to the world of music. And who knows, maybe they'll be playing Rachmaninoff by the time they're five. Or maybe they'll just enjoy banging on the keys. Either way, it's all good fun!