This is so obvious and important and a key to both mental and physical health in adulthood. All the points listed are true. My fondest memories from childhood came from outdoor activities whether from interactions with neighborhood kids (maybe including a few fights) or with my family members on camping and fishing trips. It gave me skills, and feelings of independence and confidence that I took into later life. I can't imagine how dreary and lonely a child's life would be without that kind of outdoor experience.
Pretty much if I wasn't in school, eating, sleeping or doing homework, I was outside.