ffhound- No, Niagra Falls is not a day trip from Boston if you are going by car. If you are pressed for time, you can catch a cheap flight to Buffalo, see the falls, and then get back on a later flight that day. That is the quickest way, but not the most enjoyable to see Niagra falls from Beantown.

PS. If you hotel/restaurant reccomendations I am sure that myself or any other of the many BOS FTers would be willing to help.