That does not mean you will not experience discomfort, especially during the beginning stages. Pushing yourself to the limits can be a good thing and can be an effective method of improving your level of fitness. If however, running at any level becomes a chore, then maybe it's time to consider another form of exercise. Hat - a hat is a good thing in the summer to avoid sunburn and in the winter to avoid heat loss. Running is a natural extension of walking for children.
Most kids can run at the same time they walk.
Never discourage a child from running. Take advantage of any well run local School and Running Club youth programs. They often start at the elementary level. Avoid programs that are too regimented at the elementary level. Young children typically run distances they are comfortable with.