Once a child has a solid music base (preferably through many Music Together® sessions!) they may be ready for formal music study on an instrument.
Keep in mind that we don't teach children to read before they can speak and understand what is being said to them, so we don't advise formal music lessons until a child can sing and keep a beat. That way they have a basic understanding of music in their bodies before starting an instrument.
All children will have their own timing, but in general formal study begins after age 6. Rhythm Kids® is a great option as a primer for instrument study.
Informal family lessons can start at any age! Ukulele for the whole family? Yes, please!