Hi. I'm envious.
It's not a long race and you are aboard a wonderful, safe and quite fast, boat. But, offshore racing is an inherently risky pursuit. While you will probably only spend one night at sea, it may blow up and get a bit rough. Despite the latitude, it can get cold at night out there.
I would take your lead from the skipper as far as offshore gear is concerned. But, I would have my own offshore PFD, offshore jacket and offshore overalls. However, the skipper will look at the weather and he may advise you to have only coastal gear. Off shore wear is expensive and I would try to borrow some unless you intend to make a habit of blue water sailing.
Here is a link to required Cat 1 safety gear:
ISAF/ORC Offshore Special Regulations 2012 - 2013
There is some mention of personal safety gear.
Best wishes and keep us informed about your progress.