Four? Okay...Kirby's Epic Yarn
A 2D action/platformer with an adorable art style, forgiving difficultly, and minimal text.LEGO Star Wars: the complete saga
would probably be good. Forgiving difficultly 3D action/platform a silly, silent, retelling of the Star Wars movies. Worst problem should be an occasional bad camera or obtuse puzzle.
Both of the above games have drop-in/out cooperative play. Which means that at any time someone can pick up another controller and play along for awhile either to help out or just to give the little one a chance to play with daddy. Mario Kart Wii Racing game, pick up wacky items to attach fellow racers, loose physics. Good fun, I've been playing the series since the N64 version.]
Might want to save these until she's gotten her gaming feet under her.New Super Mario Bros.
Another 2D platfromer with drop-in cooperative. Ive heard it's good might be a bit more of a challenge than what you're looking for.
I've heard good things about Boom Blox
though that's more of a puzzle game.Super Smash bros. Brawl Nintendo's 2D fighting game. Up to four players. Can get very chaotic, lots of fun.
I'm sure there are others, but that should get you started.
EDIT: Have you looked at Pikmin
? strange game, more RTS than anything a fair amount of reading to get started but little after that. I'd recommend getting the second, the first has a hard deadline on some objectives to finish which might be frustrating given how long the deadline is.
SPOILER: Highlight text to read: The first game is a "shipwrecked, limited time to repair ship" plot the second is "return to strange planet in search of treasure"