Here's a a tip from the founder of VacationKids.com, Sally Black: if you can't get a booking for a beach getaway for "President's Week", what about a trip to London, with low air prices?
Granted, you'd better pack your 'brollies and your wellies-- umbrellas and boots -- and some warm clothes too. But you can have a great time even with rainy weather (and guess what: many tourists have to do just that, in summer-time.)
So forget the atmospheric conditions, and enjoy the off-season prices and lack of crowds. London has great sightseeing for kids, including the Natural History Museum and the Science Museum, both full of fun indoors (and free).
In fact, London has loads (--that's a British term--) of free activities -- see Top Free Things in London for more.
- continue to New York City