Of the games I've rented for my daughter (7 years old), this is the best I've played so far. An hour or two into it the difficult started to get away from her but after she went to bed I ended up forgoing lost oddyssey to play Monsters Vs. Aliens. Hope my friends don't read this.
My two youngest sons (8,10) are thoroughly enjoying Monsters Vs Aliens. The game provides some good instances of humor, as well as some easy to moderate puzzle solving. Thus far, there have been 5 different kids ages 8-13 that have been playing it, and they all seem enthralled by the game. If laughter and enthusiasm are prerequisites for a fun kids game then MvA engenders plenty of both. If you have kids this is a fun safe game for them to play, and is also enjoyable enough to watch, or play co-op for the the parent(s).
This is a great game for kids of almost any age. My four year old loves this game, it's a little advanced for him, so you might have to help the little one over some of the more difficult but it really does a great job of making sure you know what your doing. We went through it pretty fast, but he likes going to the beginning and starting over.
So if you looking for something for the little one to play that doesn't poor the older ones this is a great one.