If you're thinking about signing your child up for lessons (piano, violin, ballet, gymnastics) be sure you've thought it through. Children this age are totally occupied with finding out about themselves and how they relate to other people. Because of that, your toddler may not remember what he learns from one lesson to the next. Plus, the pressure to perform can be harmful for a small child.
Before you commit to a lesson, see how your child responds in a trial situation. If he's not having fun and/or doesn't look forward to going, drop it for now. Don't be discouraged: At this age, being ready (or not) for lessons has more to do with focus and temperament than intelligence and skill.