Nuno-- My DH said that you might be better off getting an elcheapo from Wally World or other discount store, and I agreed. You never know what's going to happen, and it's hard to teach very young children--albeit prodigal and musical--how to care for an instrument, since they don't reallyt have a concept of money yet. My advice for any parent is always to wait until the child can read before investing money into lessons, instruments, etc.
BUT, slightly OT, you might want to check into Kindermusik... it's a program for very small children that uses music and movement, and it's FABULOUS not only for developing a musical ear, but also for socialization and cognitive development: their philosophy is that music is integral to social, emoptional, cognitive and language development, that every child is musical, AND that the parent is the best teacher, so everything is highly focused on involving the parent and developing coordination, language, and musical skills. I HIGHLY recommend it... I trained for a liscense a few years ago, but I decided that older children werereally who I wanted to work with.
You can also look into the Suzuki method of instruction--again, highly involves the parent, but with less of a focus on play, and more on musical perfoemance skill. This is usually started with older--4 or 5 years, I think--children. I don't know a lot about Suzuki method , because I wasn't trained in it, but several of my colleagues use it for their private instruction.