My humble opinion is to nix Curves but cool on the extra cardio. Curves is
resistance training, even though it's definitely Weightlifting Lite, and would compromise your muscle recovery between BFL workouts. Muscles grow while you're resting and not allowing them recovery time could negate all your hard work and cause overtraining.
However, it's different with cardio -- one can do cardio every day with no ill effects. A common gripe about BFL is that it's not enough cardio for most women to lose fat, so adding in some extra cardio sounds like a great idea. I recently heard about a study that showed the best weight loss and maintenance is associated with 280 minutes of cardio a week, so there's plenty of room for improvement over BFL's 60 minutes/week.
Best of luck in the start of your Challenge and please keep posting about your progress! I just love a good success story!