best way transportation to boat

We have a group of 14 travelling from Maine to New York to sail with the NCL Dawn on Dec. 11. 2005. We have two small chidren 2 & 3 and also a wheelchair bound disabled person among our group. What is the best and most practical way to get to the port o' call in New York; and least costly? Due they have parking facilities that are close and secure? Fees? Bus terminal or Amtrak close by? It will take us about 5 or 6 hours to get there from here and would appreciate any suggestions on the best way to go about this? I'm stressing that we might have a snow storm or something that will cause us to miss our boat. Help!
Liz