Walk and bike. that's how I did it. And I didn't even do it every day, about three times a week worked for me, about 3 miles each time. My dh and I got a tandem bike, pulled the smallest kids in a trailer and the older ones rode their own bikes. It's a great way to spend the summer months. I also bring my oldest walking with me, and it gives us some nice alone time. But often I just hike in the woods for some solitude.
I weighed in at 195 with my last birth and I'm at 150 now. 10 more lbs to go! I try to watch my portions, too. But if you will be breatfeeding, just make sure every calorie is nutrient rich, eliminate empty calories like candy, soda, etc, but don't worry about the calorie totals until the babe is about 6mo.