Any of you folk travel to Martha's Vineyard in the winter time?

So I have a job in Martha's Vineyard starting tomorrow. I'm a PM, and I'll be traveling down from mainland early tomorrow morning. This is quite last minute, I know, but I got some shoddy info from coworkers when it came to this...to the tune of "Have you bought your ferry ticket yet?"

Anyway, I don't think I'll need my car, although it would be nice. But should I have bought my ticket ahead of time this time of the year? Am I going to be ok just showing up in the morning to ferry over? I shouldn't be there for more than the day.