wanting more active and healthy kids, but as they get older opportunity to play disappears except for a select few.

What if schools had school sponsored teams for everyone who wanted to play, in addition to the standard varsity teams. If kids were encouraged to keep playing even if they weren't elite?
Maybe not football, but basketball, soccer, quidditch, etc... help keep kids off the street or home alone, and gives them a bit more structure and incentive to do well in school.
Obviously doing that wouldn't be free, but probably better use of money than some other programs.