Young children are often active, resulting from participation in non-organized PA or free play and they are more likely to engage in free play than organized sport.
I agree with this. When I was young, even when I was participating in an organized sport, I would still get far more PA running around my neighborhood with my friends all day every day.
This includes improved social interaction and self-esteem,
When you involve yourself in PA consistently, you will start to see progress slowly but surely and over time your confidence/ self-esteem will absolutely improve dramatically.
There is increasing evidence that participation in sport can have health benefits above and beyond the physical
This is very true. Not only is PA very beneficial physically but it is equally beneficial for your mental health. It's not just about having big muscles, its about taking care of yourself.