Since most USCG Inspected Catamarans are licensed to carry 49 passengers a private charter for only 14, especially on Christmas Day could be quite costly.
If a beautiful wooden monohull 1956 yawl is an option I stongly recommend looking at S/V Nightwind
https://www.stjohndaysail.com/http://www.tripadvisor.com/Attraction_Re...in_Islands.htmlit is comfortable for group of your size - includes food, drink and snorkel gear and has been doing daysails a long time with a stellar reputation. I realize it is a monohull but it is well sailed and a good alternative if you can't find a cost effective catamaran available.
I am sure you would have a great trip.
