I need advise with loosing a LOT of weight...how does this sound to you?

I have a little over 100lbs to loose, now I know what to eat, I mainly need help with the exercising part..since it has been a long time since I have really exercised, I know I have to start slowly, so I plan to start with walking on my treadmill for like 20 mins 3 times per week, and gradually get up to daily walking for 45-60 mins, the main thing I need advice on is the strength training. I can't afford a gym membership, so I will be doing it from home. My question is would workout video's that encorperate strenght training/cardio be good to use for the strenght training part of exercising, such as "the firm video's". Right now I have a 3 year old and a 6 month old. With my 1st pregnancy, I gained around 80lbs, never lost the weight, then had another baby a couple years later, and have added another 25 lbs, so I am very obese, I currently weigh 226lbs, and I am only 4' 10" and 26 years old.and my weight loss goal is to get down to a healthy weight (around in the 120's) and also have a toned body in the end too. I have a loose hanging stomach from my pregnancy's with stretch marks,. My plan is to eat healthy,( foods that I will eat: grilled chicken with no skin, lots of veggies, fruit, whole wheat pasta, whole wheat brown rice, whole wheat bread, low fat yogurts, fat free milk, whole wheat cereals such as bran flakes, cheerios, fiber one bars, almonds, smartones and lean cuisine frozen meals, dark green leafy salads with only 2tbsp of low fat italian dressing at a time,)...so I do have the healthy eating part down (i think)...I just need to work on the exercising part, I plan to do cardio, and strenght training (by using the strenght training video's, such as "the firm body sculpting ones) Do you think this will work? I want to have a nice toned lean HEALTHY body in the end.