Technicaly, that means that being a healthy parent gives you more energy for play and activities with your child, which will make them healthier, happier kids.
But in my case, the rewards of exercising include my son finding it fun/cool to watch me panting. He even demands I ride the treadmill just so he can watch. And he enjoys the aerobic stuff I do. He sometimes immitates me but mostly he just likes seeing me move. I guess it's the same when he gets me dancing the Hokey Pokey a dozen times a day.