Do you think my child would be able to play any instrument after being introduced to notes and keys with the Little Musician?
Of course not. What it does is to familiarize a child to musical concepts like notes, note names, pitch, and their association with one another. It will give them the basics of rhythm/tempo and encourage learning to sing, among other things.
All this should help them find any musical undertaking (whether it's an instrument or not) easier as they would have some grounding in it.