From Boston I'd take the Mass Pike west to I-84 South. Take that to the NYS Thruway (I-87) south to Route 287 South to the New Jersey Turnpike (I-95 South) exiting NJ at the Delaware Memorial Bridge. You'll get around most of the city.
Now you didn't mention if your going past DC. If so consider taking i-84 to I-81 south and bypassing a huge amount of congestion (and tolls). Its a little longer, but keeps you away from NYC/DC/Baltimore heading south.
BTW - I-287 is the "loop" around NYC. It doesn't go far enough out for some hence the route I suggest and use myself to get in/out of the area.