Becoming more active

Today as a family we went out and played together in the snow. We built snowmen, went sledding and had a snowball fight. It was fun, but by the time we were done I was sore and sweaty. I need to find more ideas for 'exercise' that's disguised as fun. I don't want to just be skinnier (although I'd be fine with, about average) but I want to be in shape. I want to be able to run and play without being winded. I want to be able to get up off the floor after playing with my kids.