Is this a good diet plan?

I've been following the weight watchers diet for a few weeks now. I've also added in an exercise plan to help me lose more weight. For example the exercise I did today was: a 35 min brisk walk, 20 min of just dance on wii, and a 10 min glute and thigh intensity workout DVD. I also taught a 3 yr old dance class for 1 hour (which isn't much exercise but it's a little something). If I continue a plan like this with this amount of exercise and weight watchers... Do you think it would be effective? I'm a teen who is 5 foot tall and weighs 125ish lbs.I'm looking to lose 10 to 20 lbs