I had mine done as an adult. I wish they had been done when I was a child but my parents never suggested it and neither did I mention to them how self-conscious I was about them. I'm delighted with the results, finally I can walk down the street on a windy day with my head held up instead of looking at the ground.
For children, I think the earlier the better cos the cartilage is softer.
Do you mind me asking, is it a child or an adult you are enquiring for? Curious. Either way, I'd recommend getting a gp referral to a good plastic surgeon and having a chat with them.