Is using a scooter a good/appropriate way to get around the surface streets in Manhattan? What about getting around downtown Boston?

She is a rock star mom and is planning a road trip with 6 of our kids on an American history trip through Kansas city, Saint Louis, Williamsburg, DC. I will fly out to Boston and do the return trip NYC, Palmyra, Niagra, Kirtland, Nauvoo, and Winter Quarters (Omaha) where I and some of the kids will do a triathlon.

I was so excited when my wife said that I should ask cougarboard about this. She heard that using scooters in DC is the best way to get around. She wants to know if it would be the same in NYC and Boston. We might have room to bring scooters in our van if we'll use them more than renting in DC.