Life insurance for your child is a gift in their future. The main purpose of purchasing a life insurance policy for a child is not the death benefit. It is to protect their insurability. While your child is young and healthy, he can qualify for coverage and add increase options that can be purchased in the future without further medical underwriting.
Consider this example: Several years ago, a set of new parents purchased a life insurance policy on their healthy, newborn son. It was a relatively small policy for $100,000 death benefit and a premium of $30/month. At the age of 7, he was diagnosed with Type 1 diabetes. As a result, this child will have a difficult time purchasing a policy in adulthood without paying substantially higher premiums. However, the policy has future purchase options which will allow him to purchase additional death benefit amount without any medical questions at certain ages (18, 21, 25, 28, 30) or at a life event (marriage, the birth of his child, etc.).
Juvenile policies tend to be significantly less expensive than adult policies and there is very little medical underwriting. Therefore, it can make a special gift, especially if there is an adverse change in health. Furthermore, the policy accumulates cash on a tax favored basis that is available to the child later in life.