yeah, you can do 4-player splitscreen.
Get the official controller, it's one of the best gamepads around, quality-wise. Try to get one a different colour from your current one, helps with various 'that's my controller!' issues, though it only matters really if you're playing with kids (or immature adults). They come in white/black/blue/pink/red/green/silver and various game-based ones like Halo 3, Halo Reach and Fable III.
Wired/wireless - depends on how far you are from the TV/monitor. The wired is lighter, but the cable gets in the way obviously, and the lack of a cable makes the wireless much tidier. Obviously batteries is a consideration.