If you want to give your credit card some exercise, head out to Select CITYWALK in Hauz Khas. It's also full of great shops and restaurants, so you can spend the afternoon having a wander. Splash some more cash at DLF Avenue Saket and MGF Metropolitan Mall.
You can browse the exhibits at Mehrauli Archaeological Park, a museum with a story of its own, during your travels to New Delhi. Amble around this culturally rich area's picturesque gardens and enjoy its top-notch restaurants.