Maniya, Central Park is wonderful place. Winters occur very charming and attractive. Have you ever seen Gapstow bridge in winter? I would suggest your sister to see Gapstow bridge. but cover yourself before leave of the house. By the way, Ivy123 is entirely right at tha point, central park can offer mesmerizing views to capture in your camera. Would advice you to go and relish yourself. Wish you all the luck for your tour.
If you are visiting New York city so definitely go to see Statue of Liberty and Albany. These places in New York are very unique and wonderful again enjoy yourself and your family.