Keeping weight off, and getting toned...?

I am definatly not fat, but its summer time and i would like to shave a bit of flub off my stomach. I feel like my hips are getting bigger, and my legs are pretty big to. For exercise equipment I only have a treadmill and I want to be able to get a little more toned in the legs and stomach before school starts again. So what are some easy things I could do for exercise (including treadmill and just regular exercises) I can do? I am 14 years old, so I don't want to have to be indoors and counting carbs and everything, so is there anything i can do to be more toned and in shape but still have a good summer without stressing about what i'm eating and keeping up with tons of exercising?? please answer asap!