USCG Captain's license required?

[Grand Slam]

A good friend, who is on the Board of his yacht club asked me this question regarding the need for a USCG Captain's license. His club is sponsoring a regatta, the participating boats will anchor out from the club. His club will provide FREE shuttle service to/from the dock to the anchored boats so that the participants can participate in food & beverages and a dance that his club is providing for a fee. Club members will “donate their time as well as their boats – runabouts for the shuttle service. Question, do the operators of the shuttles need a captain's license, if so can you help me site the appropriate statute of the law. Can I assume that if the answer is affirmative that the shuttle boats would be limited to 6 passengers maximum, since the boat is an uninspected vessel.
Thank in advance for you help, Jerry