Cape May County Park and Zoo
Near Exit 11 of the Garden State Parkway in Cape May County, a small donation (it's actually free) gets the whole family into this very nice zoo with hundreds of animals over nearly 80 acres. Educational programs are available. The zoo is open all year, except for Christmas day, but only from 10 AM until 3:45 PM.
Bring walking shoes, this was a nice daytrip during our summer vacation in Ocean City, about 30 minutes north; our kids (3 and 2) loved it. Food is restricted, so if bringing little ones, they might want to eat before arriving.