The fact that most kids in America are officially unfit is pathetic. I don't blame individual kids though. I blame parents and schools. Chances are that most parents are unfit too though.
You don't need a fancy playground but they can be a fun way to get physically fit.
The solution is simple. Play (exercise) with your kids. It's a chance to bond with them, you will improve the health of both of you and it can be very fun. Go to the playground with them today and scramble around with them for an hour.