Far from a "cages beside each other" zoo, The North Carolina Zoo strives to give its residents a truly natural place to live, and they do so beautifully. There are two park zones--Africa and North America--and both are spacious and fun to explore. Animals include polar bears, bison, giraffes, elephants, zebras, wolves, and many more; if you pay attention, the vegetation is equally impressive. Other features include a series of "geyser" fountains (these fascinated E); a pay-per-visit display of oversized animatronic bugs; and a couple of fantastic playgrounds, including one with a stream and one with a "super fast" leaf slide. The kids were so happy to be outside, and E approached each new path, building, and viewing area with clear joy. They were also both pretty fascinated by park maps!
If you go, we recommend picking an overcast, temperate day (think 60-70 degrees with a chance of showers, not too hard to come by in the North Carolina spring). A friend told us to start in Africa to see the animals before the heat of the day--helpful advice that was perfect for us. Families set on exploring the play areas in the cool of the day, however, should start in North America. Plan to walk a LOT; bring what you need to make that comfortable (good shoes, sunscreen, hat, water bottle, stroller, etc.). The zoo itself features picturesque paved paths dotted with sculpture and that include many ramps of varying slopes; you can also hike a trail between park sections. As out-of-town visitors, we were glad we stayed all day--and we were equally glad we toted in snacks and drinks, making the trip much more cost effective. When planning your day trip, spend time exploring the park website in advance, as well as reading current TripAdvisor reviews. For a place this big, you'll be glad you did your research.
If you'll be staying in the area with small kids, consider a visit to the Greensboro Children's Museum. E especially adores this place, a wonderland of imaginative play with nifty outdoor classroom to boot. You can see our earlier visit here.