I thought it was multiplayer already. I've never played it.
If I were you, I'd be a little concerned about Karaoke Revolution. I've played it once, but It takes a few minutes to get the hang of. Even if you have trained to hear pitch and can read music and all that, you'll need to get the hang of portraying pitches to initially arbitrary dots on the screen.
With Pac-Man, if it's the original, you should learn whatever tricks you can perform that get the ghosts to change directions. I believe that is very helpful, though I never learned them myself.
With Puzzle Quest, I'd go to GFAQs and see if you can't get battle advice there. Do you know which versions you'll be playing? It could actually be the 360 version that's slated to be released. I'd read up on it if I were you.