OP, beware of distances. A lot of suggestions in this thread are considerably further than 2-3 hours drive (i.e., Rochester, Finger Lakes, Montreal / Vermont), if that is a hard limit for you.

If you must stay within 2-3 hours, Philadelphia is great if you want to see another city, and a lot of popular attractions are kid friendly. But I would recommend taking the train - only a bit over an hour - much faster than driving given the traffic in that part of the country. However, if you drive, you can swing by Sesame Place in Langhorne, PA on the way; very popular with kids.

If you want the countryside or something a bit sleepier, try Bucks County, PA (which is also where Sesame Place is) or the Hudson Valley. That time of year, beware of traffic to the beach areas suggested (Cape Cod, Atlantic City, Fire Island / Montauk) if you will be going at the weekend.

All very good suggestions so far though! Just depends on exactly what you are looking for in terms of excitement and driving distance.