Scars are part of our lives and soon or later each of us usually get some. Invisible scars are worse than the one we have on our skin.
Yes, kids can be cruel. If you worry about scars your child have, talk about the reason they have it and explain that they should be proud about their marks. They are survivors and they will be accepted.
Friends do not care about visible scars, they care about the invisible ones and they will be happy to celebrate how the scars are part of how we healed.
Sometimes, real superheroes live in the hearts of small children fighting big battles.