a big CF is not even necessary, because the bare minimum for Broken Sword 1 is 89 Mb (only the first CD, no music or sound files, no video files), and around 100 Mb for Broken Sword 2 (same restrictions).
From 0.7.0 you can compress the music and sound files and the first Broken Sword 2 CD can fit on a 256 Mb card (without videos).
I'd recommend playing them on a VGA PDA for a smoother game experience, but it isn't mandatory