You'd be surprised at all the ways to get in some physical activity. Just this weekend we did a bunch of yardwork together. It was one of the best workouts I've had in a while. And we all got some exercise out of it!
We also have a trampoline and occaisionally we'll all go jump together. Jumping is really good for your lymphatic system, and so can aid in weight loss (not to mention overall health).
Some evenings we put on some dance music and workout in the living room. Papai does push ups, sit ups, and some curls, and we all do jumping jacks and crunches. My two year old loves doing jumping jacks, and when our baby was just a few weeks old, she even started kicking her legs and flapping her arms when we did jumping jacks!
Exercising can be fun family time. So make a goal to get off the couch at least 3 times a week and get some physical activity as a family! You'll get family bonding time and a workout all in one shot!