As for the uniform:
Probably not a tshirt, more of a jersey shirt judging by the underarm stripe on the ref at the left.
I note pleated, beltless slacks. Standard issue Sans-a-belt by the look of them.
As for the pink whistle...perhaps it's standard issue. But some groups use them in conjunction with a cancer awareness/charity deal. Perhaps the picture was taken during such an event.
As for their age, I supposed you're never too young to start
