I had a similar situation when my son was two. I tried to play out side with him more, playing ball, go to the park, walking around to smell flowers, finding bugs, take him for a ride in the stroller, rode him on the bike. Sometimes it was hard and i only got a 10-20 minute walk because he was not in the mood after a long day. We would play head sholder knees and toes. I tired to think of thing that he would be interested in and that I could get some exercise as well. It is not the same as the gym but it felt better than nothing to me. Try jumping rope, great cardio even if for only a few minutes at first. Put some music on and dance around while you are doing laundry. I just try to get more movement in when i am at home doing chores. Best of luck to you!