Dancing would be the best cardiovascular exercise to maintain a curvier shape. Use yoga, pilates, and/or ballet for toning.
Exercise won't drastically change your body type. Those straight up and down people (like me) probably would be like that whether they exercised or not (just softer, maybe less bulky.) If you do tend to gain muscle easily, avoid excessive resistance/weight training.
I work out at home a lot & Ellen Barrett and Tracy Effinger have really good dvds for women. I'm willing to make copies for anyone who wants to try them out.