Tell your kids to stay away from them if they see them. Unlike the cuddly way they are portrayed in cartoons, they can be very dangerous and often carry rabies.
Do NOT try to confront them yourself. Call an exterminator who is experienced with raccoons or a licensed trapper.
NOTE: This DOES get expensive, so I would not rush out to do that if you only saw them once. If they are rountinely seen by your house, you may have a problem that needs attention. They do look for ways to get INSIDE your house (usually through hole in the roof or openings by damaged gutters).
The same applies for possums, also in Brooklyn, and very nasty critters!