As I've never been in to exercise that much, not the formal "now lift your arms out from your body..." type exercise, I would like to propose some realistic exercise that most mothers could do when they are out with their kids.
- Push the stroller with the child in it. Not only will you be walking, you will get some resistance training from the stroller. You should be able to do this shortly after leaving the hospital.
- Once you are comfortable with step 1 and can make it to the park from your house, if it is in walking distance, or around the park on the sidewalk if you have to drive there, move on to this step to increase resistance: Start pushing the stroller through the grass or wood chips or whatever is available. You'd be amazed at what muscle groups are used to do this.
- Have you ever gotten on the swings and swung for a while. (Swing/swang/swung/have swung, etc. I don't know which is correct) Swinging in the swings is great for the abs and the legs. But keep an eye on your kids.
- A variation on the above I discovered just today, place a toddler on your lap as you swing. You have to swing only with your legs because you are holding on to the child. Your legs get quite the workout.
- Chase your kids in games of tag. Great aerobic exercise.
- Weight lift using your kids as the weights when they are able to hold their head up by themselves. Side benefits of this includes, your weights are growing as your ability to lift them grows. Or your ability to lift them will grow as they grow. Sometimes their weight gains may outstrip your abilities for a while but since you gotta lift them, you'll catch up.