Where abouts on the Vineyard are you going to? Edgartown, Vineyard Haven, Oak Bluffs? I think it will be about 45nm.
I'm up inside Buzzards Bay but I would think that you would think you would want to come due east below the Elizabethan Islands and come up Vineyard sound.
You can get moorings in Edgartown for $40/night. You can book ahead of time online via Dockwa or they also have some first-come-first-serve moorings. Vineyard Haven has moorings as well for $45/night but we have not stayed there as we have friends in Edgartown. Both also have dock space but they're pretty busy areas where you actually tie up and I'm cheap and can't see the advantage of shelling out $250/night.
I would also pay attention to the wind forecast when you have to head back. Assuming it's the typical SW that comes up in the afternoon, you will be taking it directly on the nose as you head through Vineyard Sound between the Elizabethan's and MV.
