First, talk to the charter people and/or the travel agent. Tell them 'no boards, no trip' . Be unkind about it, as they are making enough $ out of the deal to make it happen for you.
Get any promises they make _in_writing_! Nothing is as ephemeral as a travel agent's verbal promise. Also note that Apple Charters' baggage damage insurance only covers to $250 per item if it's not a camera or jewelry . That's not replacement cost for a surfboard. Not all the airlines that Apple Charters uses specificly say they carry surfboards-
http://www.applevacations.com/jsp/airlines/
airlines.jsp
If it's a non- US airline involved in the charter, they tend to take far better care of surfboards than a US flag airline.
Shipping boards is gonna be expensive and the shipping method varies from babying the boards enroute to delivering them via surplus B-29 bomber at 15,000 feet and then moving them around the airport via forklift stuck through the bottom of the board, shish-kebab style. No guarantees except that it will be expensive.
hope that's of use