If you've got active kids, I can highly recommend a trip down to Battery Park City (my old neighborhood!) - it's one place in NY with safe, traffic-free open spaces and good playgrounds. There's a long promenade for walks with beautiful views onto the Statue of Liberty. There are a coule of cafes and child-friendly restaurants on South End Avenue, and there's the Winter Garden at the Financial Center in the middle for (a) clean bathrooms; and (b) shopping! It's a great family area generally, and you could also take the ferry from Battery Park (south of BPC), which goes to Staten Island, is very inexpensive, and you can either get off and wander around Staten Island, or stay on and do a roundtrip (about 30-40 minutes total). Great views back onto the Mahnatten skyline (although absent the World Trade Center ) You can even stay downtown - there's a very good Marriott that has decent weekend rates. Don't know where are your business meetings, so maybe not as convenient. As you can see, I am a big downtown fan. On Cortland Street is Century 21 - fantastic discount shopping, including clothes (mens, womens, and kids) and housewares. Easy access also to Chinatown - loads of fun for little ones as very brightly colored, cheap and fast and good restaurants, little shops etc. Right next door is Little Italy, also fun, especially for good coffee and pastries. Museum of the American Indian is good with kids and is also downtown (old Customs building). Union Square (14th Street) has a great Farmers Market on Wednesdays and Saturdays - all NY State produce and a wonderful "local" atmosphere - good for buying some fruit, baked goods, jams, etc. Great restaurants and cafes bordering the square. The biggest problem with little ones is that ideally all these places are walkable, but a bit too much for small children. If you're in a hurry, plan on taxis, if you're not, consult with your concierge on busses - very easy to use and with pretty logical routes (i.e., up and down avenues) with plenty to see en route.
There's plenty more downtown (I define as below 14th street) including cools shops in Tribeca and Greenwich Village, art galleries in Soho and more.
Have a great time!