There are some legal (ex-commercial) CD32 games available at:
http://www.back2roots.orgAt least there's Banshee (great shoot'em'up, but mostly same as floppy version)
But the best game to "demonstrate" CD32 there must be Beneath a Steel Sky, that's one of the greatest adventure games for Amiga, and the CD version is fully spoken (Sound so funny, when Joey says "EXTERMINATE, EXTERMINATE!" after talking about "The laws of Robotics")
(Oh, that's 64MB download...)
One other adventure game to look for is Simon the Sorcerer CD32, Guess you should find that for relatively cheap at some Amiga dealer, that's also fully spoken.
Others worth mentioning:
Pinball Illusions (Nice CD musics)
Liberation (CD musics and speech)
Super Stardust (Animations and CD musics)
Alien Breed 3D (CD audios, and, well, classic game)
Alien Breed: Tower Assault (intro animation)
Universe (Classic adventure, with CD audios, but beware of that crap re-release, which is cracked non-working HD fixed floppy version on CDr)
And about buttons, some games use quite many (Liberation and Guardian)
I guess, that depends on whether there's floppy version or not, if there is, it shouldn't require many buttons.
I remember once configuring Quake so, I could play the game with only joypad, I could do everything, walk, look around, shoot, change weapons etc
(I think, I used directionals for looking and Red & Yellow for walking forward & back)