we lucked out that a tourist offered their NYPass that still had lots of stuff on it--transport, etc.
Take a look--there are 2 diff companies/passes. If you do several museums and attractions,it may pay off.
If you have kids --what ages? they may get bored and tired and then you waste the price (they aren't cheap)
Consult the BudgetTravel Magazine forum for good articles about using the pass cards.
There is so much to see in the city that's actually free--with 3 or more, sometimes mass transit is not a good idea. I love the reg buses because kids can see, instead of the faster ride on the subway. We loved the greyline boat and perhaps you''ll be able to see the new waterfalls exhibit??