I want to have an opposite side castling game and am building a repertoire against the Caro Kann. Does black always have the option of castling queen side or is there a way to prevent that
A "plausible" way to prevent it in the line you are talking? No!
You can't always force opposite side castling. Some openings may lead to it far more frequently, like the Sicilian Dragon or the French Steinitz. But what if Black plays the Winawer or Alekhine's Defense? Two cases where opposite side castling is rare and when it does happen, like in the Winawer, it is usually Black's choice to Castle Queenside against White's Kingside castle in non-7.Qg4 lines based on what he does with the c-pawn. Trade on d4 and he is likely going kingside. Advance to c4 and he is likely headed queenside.
I want to have an opposite side castling game and am building a repertoire against the Caro Kann. Does black always have the option of castling queen side or is there a way to prevent that