Most of us came equiped at birth with our first instruments, one listed above-voice, hands for clapping, feet for ambulating, and the body for girating to Music. As a Music Educator, I can tell you that there is absolutely nothing wrong with giving a child children's toy instruments. I can also tell you that in the past few decades many other classroom Music Teachers & I have noticed a drastically sharp drop in numbers of children who are able to match pitch, ie sing on key. Much of that is that children are not sung to by the parents & family, but instead placed in front of the tv or having stereos blasting with popular stuff in which there is absolutely no melody. Also, the very early grade teachers are no longer given training in Music, & Music class is commonly being reduced or removed from elementary schools. Add all that together, & we have children who can scream but not sing.
By far, the best thing one can do is to sing to children-look directly into their eyes and sing, sing, sing. While some may not be PolitcallyCorrect, the old early childhood songs/nursery rhymes were exactly designed to help children learn pitches. The easiest interval to sing is the minor third-5th note of the major scale down to the 3rd note, or G just above middle C to the E 2 white keys down on the piano such as in "see-saw, marjorie daw." Children will imitate what they see their family do, so when you play stringed instruments, let them have fun by "helping" you to strum. Let them sit at the Piano & play. Let them handle instruments-but be sure to watch them so that no harm comes to the child or the instrument.   My 16 mo old niece was wanting to grab my favorite Feadog (whistle), I handed it to her & she stuck it in her mouth & began to breathe into it which made a couple of soft sounds, so she figured out how to make more sounds. I have her a little bamboo flute-like thing to play & took back the metal one which could be potentially dangerous, not to mention it's my fav & best in tune feadog.
My old Irish Granny kept no toys in the little old clapboard frame farmhouse in Oklahoma. When the grandkids were very young & underfoot in the kitchen (they would not be allowed into the sitting room with the menfolk!), Granny opened the bottom cupboard doors & let them go after those wonderful pots & pans Cruiser mentioned.
Cheers!