If your child is starting to learn an instrument or if the musical world is piquing their interest, you'll need kid friendly instruments around. First of all, there's no realistic reason to expect your child to know how to manage the size and range of an adult instrument. That would just make the task a whole lot harder than is necessary. There are custom-made children's violins for a reason; if they tried playing an adult violin it would be way too heavy to hold up.
Encouraging the Young Musician
It's been said that just having a wide variety of instruments and music around the house while your kid is still young actually encourages your child to explore the musical world. He/she will certainly be more comfortable taking lessons with an instrument that is already familiar. What seems to be the developmental key for getting your child to commit to learning an instrument is to begin with manageable goals so your child can succeed early on. If your child is pushed too hard too soon, he or she will have a spiteful relationship with the instrument. But if children feel like they have found their favorite instrument for themselves and that they know how to get rewarded for practicing and playing, then you'll have more promising results. At first, instruments should feel a little bit like toys.