How about Barack Obama as the bumbling Gilligan, Bill Clinton as The Skipper, George Soros or Elliot Spitzer as The Millionaire, Bill Ayers as The Professor, Bernardine Dohrn as Mary Ann, Sean Penn as The Movie Star.
Sean Penn can play the bilge waste in the boat.
Your casting instincts are pretty good, with the exception of Soros or Spitzer as Thurston Howell, III, the millionare. They’re not nearly as “Locust Valley Lockjaw” pretentious-sounding as they’d need to be. Soros sounds flat out foreign, Spitzer sounds like a moderately educated thug.
How about “Ahoy Polloi” John Kerry, with “Terayza” playing Lovey. Husband and wife in life and on screen. It’d be a hoot. She’d need a boatload of gin-soaked raisins to stay sweet enough for the duration of filming, though.