I've now lost 40-50 pounds 3 times (3 kids) this way. And whenever I need to re-lose those pesky yo-yo last ten pounds, again and again and again, this always works in about 2 weeks:
Healthy food-ESSENTIAL.
I eat big breakfast (3-400 calories w/protein, whole grains and fruit), big lunch ( 3-400 cals protein, veggies, whole grain carb), substantial 3-4pm snack ( 300 cals protein/fruit/veggie/carbs), light dinner-no more than 300 calories, protein vegis carb) NOTHING AFTER DINNER.
All food is natural, almost no sugar aside from a square of dark chocolate here and there.
Strength training 30 mins-hour and 40 minutes cardio at LEST 3 times per week , preferably 5. I use the gym, but the most amazing DVD I have when I cant' get to the gym is my Turbo Jam Booty Sculpt. It's awesome lower body and abs, but also sculpts arms. It's only 30 minutes, so I try to do 30-40 minutes of something else later in the day too-drag the kids across town in a wagon to the park...etc... DON"T SKIP THAT LATE AFTERNOON HEALTHY SUBSTANTAL SNACK! It makes you eat less for dinner, and it doesnt' allow your metabolism to slow down during that long stretch between lunch and dinner.
When the work outs are hard to squeeze in, the good diet alone will help you keep from gaining and lose faster when you do exercise. Also, GO TO BED EARLY so you can burn fat with plenty of sleep and avoid snacking at night. Not easy with little ones I KNOW, but it works.
Good luck!