Unless there has been great trauma, children simply have fewer blocks, more openness to bringing their bodies back to a state of health.
Children carry a greater acceptance of multiple realities.
They don't question, as adults usually do, that we are capable of multidimensionality, many levels of consiousness. Often, they carry memories of other dimensional experiences. Jesus said that unless you become as a child, you shall not enter into the kingdom of heaven. This is a very important point. Today, integrating your inner child is a very popular therapeutic method.