Both of those areas are a great option. The Centennial area is a little more specific regarding the exact location. The Littleton area actually runs from the Southwest area, to the Southeast area of the south Denver metro area. Regardless, in both areas are very nice, safe communities with plenty of fun, easily accessible parks, restaurants, ice cream parlors, coffee shops, gift shops...etc.
Please let me know if I may provide additional information.
303-349-5000 - Mobile