These collections of superficial blood vessels are common in children and don't mean anything. No cause is known. They sometimes go away on their own. Although laser treatment is very gentle, I don't generally perform it in children unless the child is very self-conscious, and that's not common at all. It isn't necessary to provide extra protection for them from the sun. If one of your children complains (without prompting) bitterly about being teased, you can look into laser treatment.
Best.
Dr. Rockoff